Cementitious Panels with Swellable Materials and Methods of Providing a Moisture or Water Barrier in Cementitious Panels Using Swellable Materials

ABSTRACT

Provided are cementitious panel that include a swellable material within a core layer, a dense layer, and/or a sheet of facing material that make up a cementitious panel, as well as methods of manufacturing such cementitious panels that include a swellable material and methods of providing a moisture or water barrier in a cementitious panel.

BACKGROUND

Water penetration into and through cementitious panels is an area ofmajor concern in the building and construction industry. Cementitiouspanels are generally formed of a cementitious core material thatcontains a hydraulically setting material such as gypsum, cement, or thelike. The cementitious core material is typically sandwiched betweensheets of facing material such as paper or paperboard, or woven ornon-woven fibers or filaments. Bulk water or moisture that penetratesthrough the facing material can promote the growth of organisms, such asmold and mildew, which can lead to various health conditions.Additionally, water or moisture can deteriorate the cementitious panels.For example, the composition of the panels may become dissolved in thewet environment, the cementitious core material may crack due tofreeze-thaw cycles, and/or the facing material may separate from thecementitious core material. The facing material of a cementitious panelmay be coated with a moisture barrier; however, such coatings have alimited range of properties and performance capabilities.

It would be desirable to provide cementitious panels that containpolymeric materials for improved moisture or water barrier properties;however, previous efforts of adding polymeric materials to cementitiouspanels of a nature and quantity suitable for improving moisture or waterbarrier properties have proved unsuitable for traditional productionprocesses used to form the cementitious panels. For example, previousefforts to introduce polymeric materials tended to inhibit evacuation ofmoisture from the core of the cementitious panel, interfering with thecuring process of the cementitious material in the panel and removal ofexcess moisture from the panel during kiln drying.

As a result, there remains a need for improved cementitious panels thathave improved moisture barrier properties and other performancecapabilities.

BRIEF DESCRIPTION

Aspects and advantages will be set forth in part in the followingdescription, or may be obvious from the description, or may be learnedthrough practicing the presently disclosed subject matter.

In one aspect, the present disclosure embraces cementitious panels. Anexemplary cementitious panel may include a core layer that contains acementitious material, a plurality of sheets of facing materialsurrounding the core layer, and, optionally, one or more dense layers.The plurality of sheets of facing material may include a first sheet offacing material and a second sheet of facing material. The one or moredense layers may include a first dense layer that contains acementitious material defining an interface between the core layer andthe first sheet of facing material. The one or more dense layers mayadditionally or alternatively include a second dense layer that containsa cementitious material defining an interface between the core layer andthe second sheet of facing material. The exemplary cementitious panelmay include one or more swellable materials. In various embodiments, thecore layer, the first dense layer, the second dense layer, the firstsheet of facing material, and/or the second sheet of facing material mayinclude at least one of the one or more swellable materials.

In another aspect, the present disclosure embraces methods ofmanufacturing a cementitious panel. In one embodiment, an exemplarymethod may include conveying a plurality of sheets of facing materialand a slurry of cementitious core material that contains a swellablematerial, forming a continuous length of cementitious panel materialthat includes the slurry of cementitious core material surrounded by theplurality of sheets of facing material, and cutting the continuouslength of cementitious panel material laterally to a desired length,providing a cementitious panel. In another embodiment, an exemplarymethod may include conveying a slurry of cementitious core material anda plurality of sheets of facing material, with at least one of theplurality of sheets of facing material including a swellable material,forming a continuous length of cementitious panel material that includesthe slurry of cementitious core material surrounded by the plurality ofsheets of facing material, and cutting the continuous length ofcementitious panel material laterally to a desired length, providing acementitious panel.

In yet another aspect, the present disclosure embraces methods ofproviding a moisture or water barrier in a cementitious panel. Anexemplary method may include contacting a swellable material in acementitious panel with a first quantity of moisture or water, absorbingwith the swellable material at least some of the first quantity ofmoisture or water with the swellable material swelling to at least twicethe non-swollen volume of the swellable material, at least partiallyblocking a void volume in the cementitious panel with the swellablematerial swollen from having absorbed at least some of the firstquantity of water, and preventing or mitigating a second quantity ofmoisture of water from penetrating through the void volume at leastpartially blocked by the swollen swellable material.

These and other features, aspects and advantages will become betterunderstood with reference to the following description and appendedclaims. The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments and, together with the description, serve to explain certainprinciples of the presently disclosed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure, including the best mode thereof,directed to one of ordinary skill in the art, is set forth in thespecification, which makes reference to the appended Figures, in which:

FIG. 1A schematically shows a perspective view of an exemplarycementitious panel;

FIG. 1B schematically shows a cross-sectional view of an exemplarycementitious panel;

FIG. 2 schematically shows a cross-sectional view of another exemplarycementitious panel;

FIG. 3 schematically shows an exemplary system for manufacturing acementitious panel;

FIGS. 4A and 4B show flowcharts depicting exemplary methods ofmanufacturing a cementitious panel; and

FIG. 5 shows a flowchart depicting an exemplary method of providing amoisture or water barrier in a cementitious panel.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present disclosure.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Reference now will be made in detail to exemplary embodiments of thepresently disclosed subject matter, one or more examples of which areillustrated in the drawings. Each example is provided by way ofexplanation and should not be interpreted as limiting the presentdisclosure. In fact, it will be apparent to those skilled in the artthat various modifications and variations can be made in the presentdisclosure without departing from the scope or spirit of the presentdisclosure. For instance, features illustrated or described as part ofone embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present disclosurecovers such modifications and variations as come within the scope of theappended claims and their equivalents.

The present disclosure generally provides cementitious panels thatinclude swellable materials and methods of manufacturing cementitiouspanels that include a swellable material. The swellable materials maygenerally impart desired moisture barrier properties to cementitiouspanels while maintaining breathability. In some embodiments, swellablematerials may be capable of providing a barrier to moisture thatactivates upon the swellable material being initially exposed tomoisture or water. When an initial exposure of moisture or watercontacts the swellable material, some of the moisture or water may beabsorbed by the swellable material. As the swellable material absorbsthe moisture or water, the material swells and thereby prevents ormitigates further moisture or water penetration. The swellable materialmay prevent or mitigate moisture or water from penetrating deeper intothe cementitious panel and/or to other regions of the panel beyond alocalized region where the swellable material has swollen from havingabsorbed moisture or water. Swellable materials may be effective toprevent or mitigate moisture or water penetration through pores or voidvolumes in a cementitious panel. Additionally, or in the alternative,swellable material may be effective to prevent or mitigate moisture orwater penetration through punctures, cracks, cuts, perforations, or thelike, which may arise from damage to a cementitious panel as well asfrom ordinary installation, use, or wear of the cementitious panel.

Swellable material may be included in any portion of a cementitiouspanel. For example, swellable material may be included within the coreof a cementitious panel and/ or within the facing material thatsurrounds the core. In some embodiments, a cementitious panel mayinclude what is commonly referred to as a dense layer, which describes alayer or region of the core material that generally defines an interfacebetween the core layer and the facing material. The dense layergenerally includes a cementitious material that has a similarcomposition to that of the central region of the core, but with agreater concentration of gypsum crystals and a lower concentration ofvoid volumes such as those caused by foam when forming the panel. Thisgreater concentration of gypsum crystals and lower concentration of voidvolumes corresponds to a higher density than that of the central regionof the core. In some embodiments, a swellable material may be includedin the dense layer. The dense layer may sometimes be a particularlysuitable location for swellable materials. When included in the denselayer, swellable material may prevent or mitigate excessive water ormoisture from penetrating past the facing material or the dense layer.Similarly, when included in a facing material, swellable material mayprevent or mitigate excessive water or moisture from penetrating pastthe facing material. When included in the core layer, swellable materialmay prevent or mitigate excessive water or moisture from penetratingdeeper into the core layer. Additionally, whether located in the facingmaterial, the dense layer, or the core layer, swellable material mayprevent or mitigate water or moisture from penetrating laterally throughthe cementitious panel.

Swellable material may enhance the water impermeability of the facingmaterial, for example, by initially absorbing some water, causing theswellable material to swell and at least partially block void volumeswithin the facing material. For example, in some embodiments a facingmaterial may include a polymeric film that has a network ofinterconnected pores. The swellable material may at least partiallyblock the network of interconnected pores when swollen upon initialexposure to water or moisture. In this way, the water-swellableproperties of swellable materials may generally prevent or mitigatewater or moisture from penetrating beyond a region where the swellablematerials are located. For example, in one embodiment, when located inthe facing material and/or the dense layer, the swellable material mayprevent or mitigate water or moisture from penetrating past the facingmaterial and into the core layer.

Facing materials typically are configured to provide a certain degree ofbreathability. In some embodiments, a facing material may besubstantially impervious to liquid water yet “breathable” in the senseof being pervious to water vapor and gases. For example, a facingmaterial may include pores in that allow air or moisture to migrate intoand out of the cementitious panel, while generally preventing bulk waterfrom penetrating into the panel. However, it will be appreciated that inother embodiments, facing material may be “non-breathable” in the senseof being substantially impervious to water vapor and gases. Such poresmay provide desirable breathability, but may also undesirably allowexcessive moisture or water penetration which may damage thecementitious panel, particularly under excessively wet or humidconditions.

In some embodiments, the water-swellable properties of the swellablematerials may be reversible. Swellable materials may provide a variabledegree of breathability which may mitigate or prevent moisture or waterpenetration under such excessively wet or humid conditions. That is,when in contact with water or moisture the swellable material may swellas water or moisture is absorbed, and then the swellable material maycontract as absorbed water or moisture desorbs or dissipates. The wateror moisture may desorb or dissipate when the swellable material is nolonger in contact with water or moisture, or under conditions exhibitinga lesser degree of moisture of water exposure than the previousconditions when the swellable material absorbed the water or moisture.Under dry or sufficiently lower humidity conditions, void volumes in thecementitious panel (e.g., pores or other void volumes in the facingmaterial, dense layer, and/or core layer) may allow the cementitiouspanel to exhibit a certain degree of breathability. When thecementitious panel becomes exposed to water, moisture, or higherhumidity, swellable material in the cementitious panel may absorbmoisture and swell, thereby at least partially restricting regions ofthe void volumes where the swellable material has swollen. The swellablematerial may thereby prevent or mitigate further moisture or water frompenetration through the void volumes. The degree of swelling andcorresponding restriction of void volumes may vary depending on theextent of moisture or water exposure. When moisture or water exposure islow, the swellable material may be in an unswollen state, and the voidvolumes may allow for a maximum level of breathability. As moisture orwater exposure increases in duration and/or intensity, the swellablematerial may increasingly swell and thereby increasingly restrict thepores corresponding to the increasing moisture or water exposure. As themoisture or water exposure subsides, the swellable material may releasepreviously-absorbed moisture, thereby reopening the pores and allowingbreathability to increase.

While a facing material may provide a barrier to moisture or waterpenetration to a certain extent, the continuity of the facing materialmay become interrupted by punctures, cracks, cuts, perforations, or thelike. One particular interruption to the continuity of facing materialsare fastener holes, which include holes, punctures, cracks, cuts,perforations, or the like caused by fasteners such as nails or screwsused to hang cementitious panels in place. Swellable materials includedin any one or more portions of a cementitious panel may prevent ormitigate moisture or water penetration through such fastener holes.Similarly, swellable materials may prevent or mitigate moisture or waterpenetration through other types of punctures, cracks, cuts,perforations, or the like that may exist in a cementitious panel due todamage as well as from ordinary installation, use, or wear. Swellablematerial located in the facing material may prevent or mitigate moistureof water penetration beyond the facing material, such as through poresand/or interruptions in the continuity of the facing material. Whetherlocated in the facing material, the dense layer, and/or the core,swellable material may prevent or mitigate moisture or water penetrationbeyond a localized area where the swellable material has swollen uponhaving absorbed moisture or water.

The presently disclosed swellable materials may further be coated orencapsulated to protect the swellable materials during hydration of thecementitious material, to reduce or prevent expansion during hydrationthat might negatively affect properties of the cementitious panel,and/or to ensure that these materials maintain effectiveness at the timemost needed (i.e. during penetration by fasteners to prevent waterinfiltration after installation, after long-term exposure, and/or if thepanel cracks). Ideally, the swellable materials will not expand duringproduction of the cementitious panels so as to not disrupt the integrityof the interface between the cementitious core and the facing materialand/or so as to not reduce the integrity of the core.

The coating material for the swellable materials may dissolve in waterover time but remain intact during board hydration and board drying inthe kiln. Alternatively, the coating or encapsulating material mayprotect the swellable material to prevent swelling during boardhydration but slowly dissolve or melt in water at the elevatedtemperatures, such as at a temperature where the core of the boardapproaches the boiling point of water during drying in the kiln. Anexample of such an encapsulating material includes a fully hydrolyzedpolyvinyl alcohol. Further, the coating may be formed of materials thatare stable through board production but that rupture or break upon beingpunctured by a fastener or upon sustaining other damage or stress.

In some embodiments, after exposure and conditioning during productionof the cementitious panels, the encapsulating material would,optionally, no longer fully protect the swellable material. Theswellable material would then be available to expand during waterexposure after application in the field. Alternatively, theencapsulating material could remain covering the swellable material anddissolve or rupture after application in the field.

A cementitious panel that contains a swellable material may exhibit“self-healing” properties, such that upon sustaining initial damage of aphysical or water-related nature, the swellable material may becomeactivated by a resulting exposure to moisture or water which may causethe swellable material to swell and thereby prevent or reduce thetendency for such moisture or water to penetrate further into thecementitious panel and further damage or deteriorate the panel. Forexample, when a cementitious panel is punctured by a fastener orsustains other types of damage such as cracks, cuts, perforations, orthe like, the swellable material in the panel may be exposed, and whencoming into contact with water or moisture, the exposed swellablematerial may absorb the water or moisture and thereby expand so as to atleast partially block or fill void volumes in the cementitious panel.Additionally, or in the alternative, excessive exposure to moisture orwater may eventually lead to moisture penetrating though the facingmaterial of the panel and into void volumes within the core. Regardlessof the cause, moisture or water penetrating the facing material and/orentering such void volumes may interact with and become absorbed by theswellable material, causing the swellable material to swell and therebyprevent or reduce such moisture or water from penetrating further intothe cementitious panel. In this way, the swellable material may providesome protection where punctures or other damage might otherwise allowmoisture or water to deteriorate or weaken a cementitious panel.

Any of the presently disclosed swellable materials may be utilized toprovide cementitious panels with such “self-healing” properties,including coated or encapsulated swellable materials as well asinorganic or organic swellable materials that do not have a coating orencapsulation layer. In the case of coated or encapsulated swellablematerials, the “self-healing” properties of the swellable material maybecome activated by physical damage such as a puncture or crackrupturing the coating or encapsulation layer and thereby exposing theswellable material. Additionally, or in the alternative, the“self-healing” properties may become activated by exposure to asufficiently high level of moisture or water such that the coating orencapsulation layer dissolves. In this way, a desirable level ofmoisture may be allowed to pass through the various layers of thecementitious panel, such as to allow the panel to exhibit goodbreathability, without activating the “self-healing” properties of theswellable material unless or until the coating or encapsulation layerruptures or dissolves. A balance between good breathability and“self-healing” properties may be achieved by carefully controlling thecomposition of the swellable material and the coating or encapsulationlayer thereof, as well as by carefully controlling the location andconcentration of the swellable material within the various layers of thecementitious panel.

In some embodiments, a swellable material contained within a coating orencapsulation layer may include a swellable material in the form of afluid or a swellable material dispersed in a fluid. For example, anorganic swellable material such as a swellable polymer or asuperabsorbent polymer in the form of a fluid may be contained within acoating or encapsulation layer. As another example, such an organicswellable material and/or an inorganic swellable material such as aswellable clay may be dispersed in a fluid which may be contained withina coating or encapsulation layer. When a coating or encapsulation layerruptures or dissolves, such a fluid (i.e., a swellable material in theform of a fluid or dispersed in a fluid) may flow to other areas wherethe swellable material may then swell and thereby prevent or reduce thetendency for such moisture or water to penetrate further into thecementitious panel and further damage or deteriorate the panel.

A swellable material in the form of a fluid or dispersed in a fluid mayflow by way of capillary action and/or diffusion. In some embodiments, aswellable material may flow through void volumes, punctures, cracks,cuts, perforations, or the like by way of capillary action. In this way,the swellable material may flow into other areas of such a puncture,crack, cut, perforation, or the like so as to provide “self-healing”properties at locations beyond the original location of the coated orencapsulated swellable material. Such flowability of a swellablematerial combined with its swelling capacity may allow a swellablematerial to encompass a large area of damage, regardless of the locationwithin the area of damage where the coated or encapsulated swellablematerial may have been initially located. Additionally, or in thealternative, a swellable material in the form of a fluid or dispersed ina fluid may flow through water or moisture by way of diffusion. In someembodiments, such flowability of a swellable material may allow aswellable material to flow through water or moisture by way of diffusionto areas where the swellable material is needed most, regardless of theparticular location within the area of damage where the coated orencapsulated swellable material may have been initially located.

In the case of swellable materials that do not have a coating orencapsulation layer, “self-healing” properties may be provided byselectively locating swellable material having suitable moistureabsorption properties within various layers of the cementitious panel,such that the swellable material may become activated by exposure to asufficiently high level of moisture or water and thereby prevent orreduce further penetration into the cementitious panel, while stillallowing for good breathability. For example, in some embodiments theswellable material may be located within layers of the panel thattypically do not become exposed to sufficiently high levels of moistureor water except when the panel has sustained some initial physical orwater-related damage. Additionally, or in the alternative, swellablematerial located within the core layer of a cementitious panel may bepresent in the form of a film (e.g., a porous film) upon void volumesurfaces, and as such, the swellable material may incrementally fill orblock such void volumes (and/or such pores) with increasing exposure tomoisture or water. In this way, the breathability of the panel may beretained even with some initial swelling partially blocking the voidvolumes (and/or pores), while at the same time the swellable materialmay prevent or mitigate higher levels of moisture from crossing suchfilm and migrating to other portions of the panel.

The cementitious panels presently disclosed include constructionmaterials commonly referred to as wallboard, drywall, gypsum board,cement board, backer board, fiber cement siding, roof board, and thelike. These materials may be used for interior or exterior construction.Interior uses include finishing interior walls and ceilings andproviding backing material for flooring such as tile, stone and thelike. Exterior uses include exterior siding and roofing and providingbacking material for other exterior siding or roofing materials such asstucco, masonry, shingles, and the like. Additionally, cementitiouspanels may provide fire resistance and sound control. Cementitiouspanels may be formed with any desired dimensions. Standard dimensionsfor wallboard applications typically call for panels that are about4-foot wide and about 8-feet to 16-feet long, with thicknesses of about¼-inch to 2-inches. Of course, cementitious panels may also bemanufactured according to other standard or non-standard dimensions.

The presently disclosed cementitious panels containing swellablematerial may exhibit improved resistance to moisture or water, which maycorrespond to improved useful life of the panels, particularly in moistor wet environments. The swellable materials may reduce the tendency formoisture or water to penetrate into the core of the cementitious panels.Excessive exposure to moisture or water may lead to a host of problems,including dissolution of core material or other portions of the paneland cracking from freeze-thaw cycles. Such issues may be prevented ormitigated by the swellable material at least partly blocking voidvolumes in the cementitious panel. Additionally, the swellable materialmay reduce the tendency for mold or mildew growth caused by excessivemoisture or water penetrating through void volumes in the cementitiouspanel.

The presently disclosed cementitious panels containing swellablematerial may exhibit improved fastener holding capabilities. Improvedfastener holding capabilities may be provided, for example, by swellablematerial filling void spaces between a fastener and the cementitiouspanel. For example, moisture that may pass through such void spaces mayinteract with and become absorbed by the swellable material, causing theswellable material to swell and at least partially fill the void spaces,thereby providing a tighter fit with the fastener. Such fastener holdingcapabilities may be measured, for example, using a nail pull resistancetest according to ASTM C 473-99 and/or ASTM C1396.

Cementitious panels containing swellable material may exhibit improvedstrength properties relative to cementitious panels that do not includea swellable material. For example, the swellable materials may exhibitimproved ductility and elastic modulus which may translate to improvedductility and elastic modulus of the cementitious panel. The improvedstrength properties may allow for lighter board weights. In someembodiments, the presently disclosed cementitious panels may be highlyflexible, allowing cementitious panels to be installed in curvedsurfaces such as curved walls and the like.

In some embodiments, the presently disclosed cementitious panels mayinclude materials that provide enhanced fire-resistance capabilities.For example, a cementitious panel may include filler materials,additives, and/or coatings that provide enhanced fire resistance.Swellable materials may include water-swellable and/or heat-swellable(i.e., intumescent) materials that may provide enhanced fire resistancecapabilities. When exposed to water and/or heat, as applicable, suchswellable materials may close gaps, cracks, pores and the like in acementitious panel, thereby restricting air flow needed for combustionand/or thermal transmission. In even further embodiments, water fromfire suppression sprinklers triggered during a fire may be absorbed byswellable materials in a cementitious panel, thereby restricting airflow needed for combustion. The fire-resistance capabilities of acementitious panel may be measured in accordance with ASTM E119, ULU305, UL U419, and/or UL U423 test methods, among others.

The presently disclosed cementitious panels may additionally/oralternatively include materials capable of removing volatile organiccompounds (“VOCs”) from the surrounding area such as an indoor areawhere the cementitious panels are installed. VOCs include organicchemical compounds whose composition makes it possible for them toevaporate under normal indoor atmospheric conditions of temperature andpressure, and includes any organic compound having an initial boilingpoint less than or equal to 250° C. measured at a standard atmosphericpressure of 101.3 kPa. Exemplary VOCs include propane, butane,formaldehyde, and toluene. In some embodiments, a cementitious panel mayinclude one or more materials capable of adsorbing VOCs. Additionally,or in the alternative, a cementitious panel may include a coating thatcontains one or more photocatalytic materials capable of converting VOCsto harmless substances in the presence of UV or other light irradiation.

The presently disclosed cementitious panels may include a polymeric-filmfacing material, which may provide a surface that is substantiallyimpervious to water/moisture yet breathable to water vapor or gasses.Additionally, such facing material may provide a highly smooth surfacefinish, including a level 5 drywall finish.

It will be appreciated that the features and advantages of the presentlydisclosed cementitious panels may be provided individually or incombination. Exemplary embodiments will now be discussed in furtherdetail with reference to the accompanying figures. It is understood thatterms “upstream” and “downstream” refer to the relative direction that amaterial travels with respect to a process. For example, “upstream”refers to the direction from which a material travels, and “downstream”refers to the direction to which the material travels. It is alsounderstood that terms such as “top”, “bottom”, “outward”, “inward”, andthe like are words of convenience and are not to be construed aslimiting terms. As used herein, the terms “first”, “second”, “third”,and “fourth” may be used interchangeably to distinguish one componentfrom another and are not intended to signify importance of theindividual components. The terms “a” and “an” do not denote a limitationof quantity, but rather denote the presence of at least one of thereferenced item.

Here and throughout the specification and claims, range limitations arecombined and interchanged, and such ranges are identified and includeall the subranges contained therein unless context or language indicatesotherwise. For example, all ranges disclosed herein are inclusive of theendpoints, and the endpoints are independently combinable with eachother.

Approximating language, as used herein throughout the specification andclaims, is applied to modify any quantitative representation that couldpermissibly vary without resulting in a change in the basic function towhich it is related. Accordingly, a value modified by a term or terms,such as “about”, “approximately”, and “substantially”, are not to belimited to the precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value or the precision of the methods or machines forconstructing or manufacturing the components and/or systems.

Now referring to FIGS. 1A and 1B, an exemplary cementitious panel 100 isshown. The cementitious panel 100 includes a core layer 102 thatincludes a hydraulically setting material such as gypsum, cement, or thelike, sandwiched between by a plurality of sheets of facing material104. As shown, a cementitious panel 100 may include a front sheet 106and a back sheet 108 of facing material 104.

The core layer 102 of a cementitious panel 100 may include anyhydraulically setting material, such as gypsum, synthetic gypsum,various cement types including but not limited to Portland cements(e.g., Portland blast-furnace slag cement or blast furnace cement,Portland-fly ash cement, Portland pozzolan cement, Portland silica fumecement, masonry cements, expansive cements), non-hydraulic cements,pozzolan-lime cements, slag-lime cements, supersulfated cements, calciumsulfoaluminate cements, “natural” cements, geopolymer cements, polymercements, and blends thereof. The core layer 102 may be formulated bypreparing a slurry that includes water, one or more of suchhydraulically setting materials, and other additives such as settingaccelerants, antidesiccants, waterproofing agents, dispersants, setretarders, surfactants, strength enhancers, polymers, and reinforcingmaterials such as organic or inorganic aggregates, glass fibers, and thelike.

The facing material 104 may include a paper or paperboard material,woven or non-woven fibers or filaments, and/or a polymeric-film. In someembodiments, the facing material 104 may include a polymeric-film. Boththe front sheet 106 and/or the back sheet 108 of facing material 104 mayinclude a polymeric-film. In one embodiment, the front sheet 106 offacing material 104 is a polymeric-film. When the front sheet 106 is apolymeric-film, the back sheet 108 may include a paper or paperboardfacing material, woven or non-woven fibers or filaments, and/or apolymeric-film facing material. In another embodiment, the back sheet108 is a polymeric-film. When the back sheet 108 is a polymeric-film,the front sheet 106 may include a paper or paperboard material, woven ornon-woven fibers or filaments, and/or a polymeric-film. In yet anotherembodiment, both the front sheet 106 and the back sheet 108 of facingmaterial 104 are a polymeric-film.

The cementitious panel 100 may include a dense layer 110, which mayinclude a portion of the core layer 102. The portion of the core layer102 that includes the dense layer 110 surrounds a central core layer103. The dense layer 110 may be formed by applying a coating ofcementitious material to the inner side of the facing material 104. Thecoating may be applied to the front sheet 106 and/or to the back sheet108 so as to provide a dense layer at an interface between the corelayer 102 and the front sheet 106 and/or between the core layer and theback sheet 108. As shown in FIG. 1B, a cementitious panel may include afront dense layer 112 and a back dense layer 114. The coating that makesup the dense layer 110 typically includes a higher concentration ofgypsum crystals and a lower concentration of void volumes relative tothe central core layer 103. In some embodiments, some of the gypsumcrystals that form in the dense layer 110 may penetrate into the facingmaterial 104, which helps to bind the facing material 104 to the corelayer 102. An adhesive or binder may also be included in the core layer102 and/or in the dense layer 110 to help adhere the facing material 104to the core layer 102. The adhesive or binder may include starch,dextrin, polyester resin, poly(vinly acetate), poly(ethylene-co-vinylacetate), polyvinyl alcohol, styrene butadiene, epoxies, acrylics,polyimides, polyurethanes, and so forth.

Typically, cementitious panels 100 commonly referred to as wallboard,drywall, gypsum board, and the like are formed from a cementitious corelayer 102 that primarily contains gypsum. Gypsum commonly refers to amineral composed primarily of calcium sulfate dihydrate, which has thechemical formula CaSO₄·2H₂O. Gypsum may be obtained from naturallyoccurring calcium sulfate in anhydrous, dihydrate, or hemihydrate state.Alternatively, gypsum may be obtained synthetically, from industrialscrubbers using a flue-gas desulfurization process. A slurry of gypsumto be used as a core layer 102 for a cementitious panel may be formed bymixing water with powdered anhydrous calcium sulfate (CaSO₄) and/orcalcium sulfate hemihydrate (CaSO₄·½H₂O), commonly referred to ascalcined gypsum, stucco, or plaster of Paris. Calcined gypsum istypically prepared by heating pulverized uncalcined gypsum rock in amill such as a rotary kiln, hammer mill, impact mill, and others orsimultaneously heating and pulverizing uncalcined gypsum in a mill toyield stucco predominately including calcium sulfate hemihydrate and torelease water vapor. Calcined gypsum (i.e., calcium sulfate hemihydrate)has the desirable property of being chemically reactive with water andwill “set” rather quickly when the two are mixed together, yieldingcalcium sulfate dihydrate.

Typically, cementitious panels 100 commonly referred to as cement board,backer board, fiber cement siding, and the like are formed from acementitious core layer 102 that primarily contains Portland cement andorganic or inorganic aggregate. Portland cement commonly refers to ablend of hydraulically setting materials that primarily includeshydraulic calcium silicates (3CaO·SiO₂ and 2CaO·SiO₂). Additionally,Portland cement may include one or more forms of calcium sulfate,magnesium oxide, aluminum oxide, and iron oxide. Organic aggregateincludes cellulose fibers, wood flakes, and the like.

As shown in FIG. 2 , the cementitious panel 100 may include a facingmaterial 104 that has a plurality of layers. It will be appreciated thatany number of layers of facing material 104 may be provided. Forexample, as shown, a cementitious panel may include a front sheet 106and a back sheet 108 of facing material 104, and the front sheet 106 mayinclude a plurality of layers such as a first layer 116 and a secondlayer 118. However, it will be appreciated that both front sheet 106and/or the back sheet 108 of facing material 104 may include a pluralityof layers. A swellable material may be provided in any one or morelayers of facing material 104. In some embodiments, a swellable materialmay be provided in the first layer 116 of the facing material, which maybe an outer layer of the facing material. A swellable material in thefirst layer 116 may provide a moisture or water barrier to thecementitious panel.

The plurality of layers may be provided by adhering sheets of facingmaterial to one another, and/or by applying a coating to a sheet offacing material 104. An adhesive or binder may be included to adheremultiple layers of facing material 104 to one another, and/or to adherethe facing material 104 to the core layer 102. The adhesive or bindermay be applied separately or may be included within the composition ofany of the layers, such as within the composition of the facing material104 or within the composition of the dense layer 110. The multiplelayers of facing material may include any desired type of material,including a polymeric-film facing material, a paper or paperboardmaterial, and/or woven or non-woven fibers or filaments. In someembodiments, one or more of the plurality of layers of facing material104 may take the form of a coating. For example, a coating may beapplied to the first layer 116 of facing material 104 and/or to thesecond layer 118 of facing material 104. In some embodiments, the firstlayer 116 of facing material 104 may take the form of a coating appliedto the second layer 118 of facing material 104. The coating may beapplied to a layer of facing material 104 that takes the form of apolymeric-film material, a paper or paperboard material, and/or woven ornon-woven fibers or filaments.

Swellable Materials

Cementitious panels may be provided that include any one or more of anumber of different kinds of swellable materials. The term “swellablematerial” refers to an organic or inorganic material, or a combinationof organic and/or inorganic materials, that include at least onecomponent that is “water-swellable.” By “water-swellable,” it is meantthat the particles have a capacity to swell when contacted with moistureor water. The term “organic” refers to a natural or syntheticcarbon-based compound or material, and the term “inorganic” refers toany compound or material that is not organic. In accordance with thepresent disclosure, a swellable material may include one or more organicswellable materials and/or inorganic swellable materials. Exemplaryswellable materials include organic swellable materials such asswellable polymers and superabsorbent polymers, inorganic swellablematerials such as swellable clays, and combinations thereof. Furtherexemplary swellable materials include composite swellable materials suchas superabsorbent particles, and coated or encapsulated swellablematerials.

Exemplary swellable materials may have a swelling capacity of at leasttwice the non-swollen volume of the swellable material, as determined byvolumetric expansion. For example, in some embodiments, a swellablematerial may have capability to swell to a volume that is from 2 to 100times the non-swollen volume of the swellable material, such as from 2to 50 times the non-swollen volume, such as from 2 to 25 times thenon-swollen volume, such as from 2 to 5 times the non-swollen volume,such as from 2 to 10 times the non-swollen volume, such as from 5 to 25times the non-swollen volume, such as from 10 to 30 times thenon-swollen volume, such as from 20 to 50 times the non-swollen volume,such as from 40 to 60 times the non-swollen volume, such as from 50 to80 times the non-swollen volume of the swellable material. A swellablematerial may swell to a volume that is at least 2 times the non-swollenvolume of the swellable material, such as at least 5 times thenon-swollen volume, such as at least 5 times the non-swollen volume,such as at least 10 times the non-swollen volume, such as at least 20times the non-swollen volume, such as at least 30 times the non-swollenvolume, such as at least 40 times the non-swollen volume, such as atleast 50 times the non-swollen volume, such as at least 60 times thenon-swollen volume, such as at least 80 times the non-swollen volume ofthe swellable material. A swellable material may swell to a volume thatis less than 80 times the non-swollen volume of the swellable material,such as less than 65 times the non-swollen volume, such as less than 55times the non-swollen volume, such as less than 45 times the non-swollenvolume, such as less than 35 times the non-swollen volume, such as lessthan 25 times the non-swollen volume, such as less than 15 times thenon-swollen volume, such as less than 10 times the non-swollen volume,such as less than 5 times the non-swollen volume of the swellablematerial.

Exemplary swellable materials may additionally or alternatively havecapability to absorb an amount of water that exceeds the weight of theswellable material. For example, an exemplary swellable material mayhave the capacity to absorb from 2 to 30 times its weight in distilledwater, such as from 2 to 5 times its weight, such as from 2 to 10 timesits weight, such as from 4 to 10 times its weight, such as from 8 to 20times its weight, such as from 10 to 15 times its weight, such as from15 to 30 times its weight, such as from 20 to 30 times its weight indistilled water. Exemplary swellable material may have the capacity toabsorb at least 2 times its weight in distilled water, such as at least4 times its weight, such as at least 5 times its weight, such as atleast 8 times its weight, such as at least 10 times its weight, such asat least 15 times its weight, such as at least 20 times its weight, suchas at least 30 times its weight in distilled water. The particularswellable materials used may be selected based on the specificapplication and performance requirements thereof. Such swellablematerials are typically capable of being dispersed in the form ofparticles and/or discrete domains of a micro-scale and/or nano-scalesize. The micro-scale and/or nano-scale particles and/or domains mayhave any one or more of a variety of different shapes, includingcylindrical, elliptical, flake-like, nodular, platelike, spherical,tubular, fibrous, branched, and so forth. The shape (or morphology) ofswellable materials in the form of particles may vary depending upon thespecific application. For example, generally spherical morphologies(such as solid beads, microbeads, or hollow spheres), can be used, aswell as particles that are cubic, platy, acicular (elongated or fibrous)or lamellar. Additionally, the swellable particles and/or discretedomains may have an internal structure that is hollow, porous and/orvoid free; e.g., a hollow center with porous or solid walls, and soforth.

The size of the particles and/or discrete domains of swellable materialmay be controlled to optimize performance for a particular application.Swellable materials of a particular size may be formed by any of anumber of various methods known in the art, including pulverizing andclassifying dry particulate material, crystallization, precipitation,gas phase condensation, chemical attrition, etc. As an example, bulkswellable materials may be milled with milling media to a micro-scaleand/or nano-scale size in the presence of a solvent (water and/or anorganic solvent) and optionally in the presence of a polymeric grindresin and/or a dispersant. Either hydrophobic or hydrophilic dispersantscan be used depending on the particular swellable material.

In some embodiments, particles and/or discrete domains of swellablematerial may have a micro-scale size characterized by an averagecross-sectional dimension from 1 µm to 2000 µm, such as from 5 µm to1,000 µm, such as from 10 µm to 500 µm, such as from 50 µm to 500 µm.The average cross-sectional dimension may be greater than 1 µm, such asgreater than 10 µm, such as greater than 25 µm, such as greater than 50µm, such as greater than 100 µm, such as greater than 200 µm, such asgreater than 300 µm, such as greater than 700 µm, such as greater than1100 µm, such as greater than 1600 µm, such as greater than 1800 µm. Theaverage cross-sectional dimension of such micro-scale particles and/ordiscrete domains may be 2000 µm or less, such as 1800 µm or less, suchas 1500 µm or less, such as 1200 µm or less, such as 900 µm or less,such as 600 µm or less, such as 300 µm or less, such as 100 µm or less,such as 75 µm or less, such as 45 µm or less, such as 15 µm or less,such as 5 µm or less.

Additionally, or in the alternative, in some embodiments, particlesand/or discrete domains of swellable material may have a nano-scale sizecharacterized by an average cross-sectional dimension from 1 nm to 1,000nm, such as from 5 nm to 800 nm, such as from 10 nm to 500 nm, such asfrom 20 nm to 200 nm. The average cross-sectional dimension may begreater than 1 nm, such as greater than 10 nm, such as greater than 25nm, such as greater than 50 nm, such as greater than 100 nm, such asgreater than 200 nm, such as greater than 300 nm, such as greater than500 nm, such as greater than 700 nm, such as greater than 900 nm. Theaverage cross-sectional dimension of such micro-scale particles and/ordiscrete domains may be 1,000 nm or less, such as 950 nm or less, suchas 750 nm or less, such as 550 nm or less, such as 350 nm or less, suchas 150 nm or less, such as 90 nm or less, such as 70 nm or less, such as55 nm or less, such as 35 nm or less, such as 15 nm or less, such as 5nm or less.

A swellable material may be employed in any desired amount. The amountof swellable material may be described with reference to theconcentration of swellable material in the segment of the cementitiouspanel containing the swellable material. For example, the amount ofswellable material may be described as a weight percentage of the corematerial, the facing material, or the dense layer, as applicable.Regardless of whether the swellable material is employed in the corematerial, the facing material, or the dense layer, the concentration ofthe swellable material in such segment may range from 0.1 wt. % to 90wt. % of such segment, such as from 1 wt. % to 90 wt. %, such as from 1wt. % to 75 wt. %, such as from 5 wt. % to 65 wt. %, such as from 10 wt.% to 60 wt. %, such as from 20 wt. % to 50 wt. %, such as from 30 wt. %to 40 wt. % based on the total weight of the applicable segment. In someembodiments, a swellable material may be employed in an amount rangingfrom 0.1 wt. % to 25 wt. %, such as from 0.5 wt. % to 25 wt. %, such asfrom 1 wt. % to 25 wt. %, such as from 5 wt. % to 20 wt. %, such as from10 wt. % to 20 wt. % based on the total weight of the applicablesegment. In another embodiment, a swellable material may be employed inan amount ranging from 25 wt. % to 75 wt. %, such as from 40 wt. % to 70wt. %, such as from 50 wt. % to 70 wt. %, such as from 55 wt. % to 65wt. % based on the total weight of the applicable segment. The swellablematerial may be employed in an amount of at least 1%, such as at least10%, such as at least 20%, such as at least 30%, such as at least 40%,such as at least 50%, such as at least 60%, such as at least 70%, basedon the total weight of the applicable segment. The swellable materialmay be employed in an amount of less than 100%, such as less than 90%,such as less than 80%, such as less than 75%, such as less than 65%,such as less than 60%, such as less than 55%, such as less than 45%,such as less than 40%, such as less than 30%, such as less than 20%,such as less than 10%, such as less than 5%, based on the total weightof the applicable segment.

A. Inorganic Swellable Materials

Suitable inorganic swellable materials include clays or siliceousmaterials, as well as particles of aluminum oxides, titanium oxides(e.g., titanium dioxide), zinc oxides, antimony oxides, zirconia,magnesia, zinc sulfide, barium sulfate, strontium sulfate, cesium oxide,yttrium oxide, colloidal yttria, zirconia, colloidal zirconia, calciumcarbonate, and/or magnesium carbonate. Additional suitable inorganicswellable materials include aluminum hydroxide (ATH), magnesiumhydroxide (MDH), refractory fibers (e.g. alumina or zirconia), magnesiumphosphate pentahydrate, magnesium sulfate heptahydrate, zinc borate,magnesium carbonate basic pentahydrate, hydromagnesite, sodium boratedecahydrate, perlite, intumescents, and melamine polymers. Exemplaryinorganic swellable materials may exist in the form of layers includinga combination of tetrahedral sheets and octahedral sheets. Someswellable materials may have a 2:1 ratio of octahedral sheets totetrahedral sheets. Some swellable materials may include a combinationof inorganic materials including one or more inorganic materials thatindividually are not swellable. However, it will be appreciated thatparticles or discrete domains that include an inorganic material that isnot swellable will nevertheless be regarded as a swellable material whensuch particles or discrete domains as a whole have a capacity to swellwhen contacted with moisture or water. As an example, some materialsthat have a capacity to swell when contacted with water have a 2:1 ratioof octahedral sheets to tetrahedral sheets, while some materials thatlack as capacity to swell when contacted with water have a 1:1 ratio ofoctahedral sheets to tetrahedral sheets. A combination of such materialsmay nevertheless be regarded as a swellable material, at least because aportion of the material has a capacity to swell when contacted withwater.

In some embodiments, siliceous particles may be particularly suitableswellable materials. Examples of suitable siliceous particles includeparticles of crystalline or amorphous phyllosilicates and micaceousminerals, including fumed silica, amorphous silica, colloidal silica,and surface-modified silica. Suitable phyllosilicates include, forexample, beidelite, hectorite, kenyaite, laponite, magadite, medmontite,montmorillonite, nontronite, phlogopite, saponite, sauconite, smectite,stevensite, vermiculite, and volkonskoite, as well as combinations ofany of the foregoing. Smectite and vermiculite are particularlysuitable, as these materials have a pronounced ability to adsorb water.Suitable smectite particles include montmorillonite (often referred toas bentonite), beidelite, nontronite, hectorite, saponite, sobockite,svinfordite, sauconite, and laponite, as well as montmorillonite salts,such as sodium montmorillonite, magnesium montmorillonite, calciummontmorillonite, arcillite (i.e., calcined montmorillonite), and soforth.

Further suitable phyllosilicates include kaolin minerals (includingkaolinite, dickite, and hacrite); micaceous minerals (e.g., illite) andmixed illite/smectite minerals, such as rectorite, tarosovite, ledikiteand admixtures of illites with the phyllosilicates named above;serpentine minerals, chlorite minerals, sepolite, palygorskite, andbauxite, as well as combinations of any of the foregoing. Additionalsuitable siliceous materials include talc, gypsum, calcite, diatomaceousearth, natural and synthetic zeolites, cement, calcium silicate, sodiumaluminum silicates (e.g., nonzeolite silicates), aluminum polysilicate,magnesium silicates, wollastonite, alumina silica gels, glass particles,pumice, tuff, and the like. Of the silicas, precipitated silica, silicagel, or fumed silica may be particularly suitable. In addition, thesilica may be a surface-modified silica.

Suitable inorganic swellable materials may additionally include metalnanoparticles or fibers, such as molybdenum, platinum, palladium,nickel, aluminum, copper, gold, iron, silver, alloys of any of theforegoing, as well as combinations or mixtures of any of the foregoing.In some embodiments, an inorganic swellable material may include metalfibers, such as aluminum, copper, or steel metal fibers. Exemplaryaluminum particles include alumina, colloidal alumina, fumed alumina,and calcined alumina. Further suitable inorganic swellable materialsinclude graphite; ceramic materials; carbides; nitrides, such as boronnitride; borides; sulfides, such as molybdenum disulfide, tantalumdisulfide, tungsten disulfide, silver sulfide, and zinc sulfide; as wellas combinations of any of the foregoing.

Another type of inorganic material that may be included in a swellablematerial includes inorganic polymeric materials. In one embodiment, aswellable material may include an inorganic polymeric material.Inorganic polymeric materials include polymeric materials that have abackbone chain with a repeating unit based on an element other thancarbon, such as Al, B, Fe, Ge, N, O, P, S, Si, Sn, as well ascombinations of these, such as combinations of N and P, Si and O, S andN, Fe and Si, Al and O, and so forth. Inorganic polymeric materials mayinclude homopolymers, copolymers, random copolymers, block copolymers,graft copolymers, atactic polymers, isotactic polymers, syndiotacticpolymers, linear polymers, and/or branched polymers. When mixtures ofpolymers are used, the mixture may be homogeneous, or the mixture mayinclude two or more polymeric phases. As examples, suitable inorganicpolymeric swellable materials include polyphosphazenes, polysilanes,polysiloxanes, polygermanes, polymeric sulfur, polymeric selenium,silicones, aluminum-containing polymers (e.g., poly(acyloxyaloxane),poly(aluminoxane)), ferrocene-containing polymers (e.g.,poly(ferrocenylsilanes)), as well as combinations of any of theforegoing.

Still another type of inorganic material that may be included in aswellable material includes inorganic pigments. In one embodiment, aswellable material includes an inorganic pigment. Example inorganicpigments include aluminum-containing pigments (e.g., zeolite-basedminerals), antimony-containing pigments (e.g., antimony(III) oxide),arsenic-containing pigments (e.g., realgar), barium-containing pigments(e.g., barium sulfate), bismuth-containing pigments, cadmium-containingpigments (e.g., cadmium sulfide), carbon-containing pigments (e.g.,carbon black), chromium-containing pigments (e.g., chromium(III) oxide,lead(II) chromate), cobalt-containing pigments (e.g., cobalt phosphate,cobalt(II) oxide-aluminum oxide, cobalt(II) aluminate),copper-containing pigments (e.g., barium-copper-silicates, calciumcopper silicate, azurite), iron-containing pigments (e.g., ochre, leadantimonate), lead-containing pigments (e.g., minium, lead(II)carbonate), manganese-containing pigments (e.g., YInMn, manganese(IV)oxide), mercury-containing pigments (e.g., mercuric sulfides),silica-containing pigments, tin-containing pigments (e.g., tin(IV)sulfide), titanium-containing pigments (e.g., titanium(III) oxide,titanium(IV) oxide), and zinc-containing pigments (e.g., zinc chromate,zinc oxide).

1. Inorganic Swellable Materials With Organic Surface Treatments

In some embodiments, exemplary inorganic swellable materials may containan organic surface treatment. In some embodiments, an organic surfacetreatment may improve bonding between the swellable material with thefacing material 104 or the core layer 102 and/or may prevent expansionof the swellable material during board formation. In one embodiment, theorganic surface treatment may be formed from a quaternary onium (e.g.,salt or ion). In the case of swellable materials with a layeredstructure, the organic surface treatment may become intercalated viaion-exchange into the interlayer spaces between adjacent layers ofswellable material. The quaternary onium ion may have the followingstructure:

wherein

-   X is N, P, S, or O; and-   R₁, R₂, R₃ and R₄ are independently hydrogen or organic moieties,    such as linear or branched alkyl, aryl or aralkyl moieties having 1    to about 24 carbon atoms.

Particularly suitable quaternary ammonium ions are those having thestructure below:

wherein

R₁ is a long chain alkyl moiety ranging from C₆ to C₂₄, straight orbranched chain, including mixtures of long chain moieties, such as C₆,C₈, C₁₀, C₁₂, C₁₄, C₁₆, C₁₈, C₂₀, C₂₂ and C₂₄, alone or in anycombination; and R₂, R₃ and R₄ are moieties, which may be the same ordifferent, selected from the group consisting of H, alkyl, hydroxyalkyl,benzyl, substituted benzyl, e.g., straight or branched chainalkyl-substituted and halogen-substituted; ethoxylated or propoxylatedalkyl; ethoxylated or propoxylated benzyl (e.g., 1-10 moles ofethoxylation or 1-10 moles of propoxylation).

Additional useful multi-charged spacing/coupling agents include forexample, tetra-, tri-, and di-onium species such as tetra-ammonium,tri-ammonium, and di-ammonium (primary, secondary, tertiary, andquaternary), -phosphonium, -oxonium, or -sulfonium derivatives ofaliphatic, aromatic or arylaliphatic amines, phosphines, esters,alcohols and sulfides. Illustrative of such materials are di-oniumcompounds of the formula:

wherein

-   X+ and Y +, are the same or different and are ammonium, sulfonium,    phosphonium, or oxonium radicals such as —NH(CH₃)₂ ⁺, —NH₂(CH₃)⁺, —    N(CH₃)₃ ⁺, —N(CH₃)₂(CH₂CH₃)⁺, —N(CH₃)(CH₂CH₃)₂ ⁺, —S(CH₃)₂ ⁺,    —S(CH₃)₂ ⁺, —P(CH₃)₃ ⁺, —NH₃ ⁺, etc.;-   R is an organic spacing, backbone radical, straight or branched,    such as those having from 2 to 24 carbon atoms, and in some    embodiments from 3 to 10 carbon atoms, in a backbone organic spacing    molecule covalently bonded at its ends to charged N⁺, P⁺, S⁺ and/or    O⁺ cations; and-   R¹ can be hydrogen, or a linear or branched alkyl radical of 1 to 22    carbon atoms, linear or branched, and in some embodiments, 6 to 22    carbon atoms.

Exemplary R groups are alkyls (e.g., methyl, ethyl, butyl, octyl, etc.);aryl (e.g., benzyl, phenylalkyl, etc.); alkylenes (e.g., methylene,ethylene, octylene, nonylene, tert-butylene, neopentylene, isopropylene,sec-butylene, dodecylene, etc.); alkenylenes (e.g., 1-propenylene,1-butenylene, 1-pentenylene, 1-hexenylene, 1-heptenylene, 1-octenylene,etc.); cycloalkenylenes (e.g., cyclohexenylene, cyclopentenylene, etc.);hydroxyalkyl (e.g. hydroxymethyl, hydroxyethyl, hydroxyl-n-propyl,hydroxyisopropyl, hydroxyl-n-butyl, hydroxyl-iso-butyl,hydroxyl-tert-butyl, etc.), alkanoylalkylenes (e.g., butanoyloctadecylene, pentanoyl nonadecylene, octanoyl pentadecylene, ethanoylundecylene, propanoyl hexadecylene, etc.); alkylaminoalkylenes (e.g.,methylamino octadecylene, ethylamino pentadecylene, butylaminononadecylene, etc.); dialkylaminoalkylene (e.g., dimethylaminooctadecylene, methylethylamino nonadecylene, etc.); arylaminoalkylenes(e.g., phenylamino octadecylene, p-methylphenylamino nonadecylene,etc.); diarylaminoalkylenes (e.g., diphenylamino pentadecylene,p-nitrophenyl-p′methylphenylamino octadecylene, etc.);alkylarylaminoalkylenes (e.g., 2-phenyl-4-methylamino pentadecylene,etc.); alkylsulfinylenes, alkylsulfonylenes, alkylthio, arylthio,arylsulfinylenes, and arylsulfonylenes (e.g., butylthio octadecylene,neopentylthio pentadecylene, methylsulfinylnonadecylene, benzylsulfinylpentadecylene, phenylsulfinyl octadecylene, propylthiooctadecylene,octylthio pentadecylene, nonylsulfonyl nonadecylene, octylsulfonylhexadecylene, methylthio nonadecylene, isopropylthio octadecylene,phenylsulfonyl pentadecylene, methylsulfonyl nonadecylene, nonylthiopentadecylene, phenylthio octadecylene, ethyltio nonadecylene,benzylthio undecylene, phenethylthio pentadecylene, sec-butylthiooctadecylene, naphthylthio undecylene, etc.); alkoxycarbonylalkylenes(e.g., methoxycarbonylene, ethoxycarbonylene, butoxycarbonylene, etc.);cycloalkylenes (e.g., cyclohexylene, cyclopentylene, cyclooctylene,cycloheptylene, etc.); alkoxyalkylenes (e.g., methoxymethylene,ethoxymethylene, butoxymethylene, propoxyethylene, pentoxybutylene,etc.); aryloxyalkylenes and aryloxyarylenes (e.g., phenoxyphenylene,phenoxymethylene, etc.); aryloryalkylenes (e.g., phenoxydecylene,phenoxyoctylene, etc.); alylalkylenes (e.g., benzylene, phenthylene,8-phenyloctylene, 10-phenyldecylene, etc.); alkylarylenes (e.g.,3-decylphenylene, 4-octylphenylene, 4-nonylphenylene, etc.); andpolypropylene glycol and polyethylene glycol substituents (e.g.,ethylene, propylene, butylene, phenylene, benzylene, tolylene,p-styrylene, p-phenylmethylene, octylene, dodecylene, octadecylene,methoxyethylene, etc.), as well as combinations thereof. Such tetra-,tri-, and di-ammonium, -sulfonium, -phosphonium, -oxonium;ammonium/sulfonium; ammonium/phosphonium; ammonium/oxonium;phosphonium/oxonium; sulfonium/oxonium; and sulfonium/phosphoniumradicals are well known in the art and can be derived from thecorresponding amines, phosphines, alcohols or ethers, and sulfides.

Particularly suitable multi-charged spacing/coupling agent compounds aremulti-onium compounds that include at least two primary, secondary,tertiary or quaternary ammonium, phosphonium, sulfonium, and/or oxoniumions having the following general formula:

wherein

-   R is an alkylene, aralkylene or substituted alkylene charged atom    spacing moiety; and-   Z₁, Z₂, R₁, R₂, R₃, and R₄ may be the same or different and selected    from the group consisting of hydrogen, alkyl, aralkyl, benzyl,    substituted benzyl (e.g., e.g., straight or branched chain    alkyl-substituted and halogen-substituted); ethoxylated or    propoxylated alkyl; ethoxylated or propoxylated benzyl (e.g., 1-10    moles of ethoxylation or 1-10 moles of propoxylation).

Particularly suitable organic cations may include, for instance,quaternary ammonium compounds, such as dimethyl bis[hydrogenated tallow]ammonium chloride (2M2HT), methyl benzyl bis[hydrogenated tallow]ammonium chloride (MB2HT), methyl tris[hydrogenated tallow alkyl]chloride (M3HT), etc. An example of a suitable inorganic swellablematerial is Nanomer™ 1.44P, which is a quaternary ammonium modifiedmontmorillonite and commercially available from Nanocor, Inc. Othersuitable inorganic swellable materials include those available fromSouthern Clay Products, such as Cloisite™ 15A, Cloisite™ 30B, Cloisite™93A, and Cloisite™ Na⁺.

B. Organic Swellable Materials

Examples of organic swellable materials include without limitationnatural and synthetic superabsorbent materials. Natural superabsorbentmaterials include guar gum, agar, pectin, cellulosic fibers includingultrafine cellulose, nanocrystalline cellulose, and microcrystallinecellulose, and the like. Synthetic superabsorbent materials includesuperabsorbent polymers such as alkali salts of polyacrylic acids,polyacrylamides, polyvinyl alcohol, ethylene-maleic anhydridecopolymers, polyvinyl ethers, nanocrystalline cellulose,microcrystalline cellulose, methyl cellulose, carboxymethyl cellulose,hydroxypropylcellulose, hydroxypropylmethylcellulos,polyvinylmorpholinone, and polymers and copolymers of vinyl sulfonicacid, polyacrylates, polyacrylamides, polyvinylpyrridine, and the like.Exemplary alkali salts of polyacrylic acids include poly(acrylicacid)-potassium salt, poly(acrylic acid)-sodium salt, poly(acrylicacid-co-acrylamide)-potassium salt, poly(acrylic acid)-sodiumsalt-graft-poly(ethylene oxide), poly(2-hydroxyethyl methacrylate),poly(2-hydroxypropyl methacrylate), and poly(isobutylene-co-maleicacid)-sodium salt. Exemplary microcrystalline cellulose includesultrafine cellulose, colloidal cellulose, and nanocrystalline ormicrocrystalline cellulose gel, which are available, for example, fromJ. Rettenmaier USA LP under the designations VITAPUR®, VITACEL®, andABROCEL®. Other suitable polymers include hydrolyzed acrylonitrilegrafted starch, acrylic acid grafted starch, and isobutylene maleicanhydride polymers and mixtures thereof. Superabsorbent polymers maypreferably be lightly crosslinked to render the materials substantiallywater insoluble. Crosslinking may, for example, be accomplished byirradiation or by covalent, ionic, van der Waals, or hydrogen bonding.

An exemplary superabsorbent polymer may be capable of absorbing at least10 times its weight in distilled water, such as at least 50 times itsweight, such as at least 100 times its weight, such as at least 300times its weight, such as at least 400 times its weight, such as atleast 500 times its weight, such as at least 700 times its weight, suchas at least 1,000 times its weight in distilled water. Superabsorbentpolymers are generally formed from a three-dimensional crosslinkedpolymer network that contains repeating units derived from one or moreethylenically (e.g., monoethylenically) unsaturated monomeric compoundshaving at least one hydrophilic radical, such as a carboxyl, carboxylicacid anhydride, carboxylic acid salt, sulfonic acid, sulfonic acid salt,hydroxyl, ether, amide, amino, or quaternary ammonium salt group. Thesemonomeric compounds can be selected, for example, from ethylenicallyunsaturated carboxylic acids and acid anhydrides, ethylenicallyunsaturated sulfonic acids, and mixtures thereof.

In some embodiments, a swellable material may include a superabsorbentpolymer that includes an ethylenically unsaturated carboxylic acidmonomeric compound. Suitable ethylenically unsaturated carboxylic acidand carboxylic acid anhydride monomeric compounds for formingsuperabsorbent polymers include, for example, acrylic acid, methacrylicacid, ethacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid,crotonic acid (β-methylacrylic acid), α-phenylacrylic acid,β-acryloxy-propionic acid, sorbic acid, α-chlorosorbic acid, angelicacid, cinnamic acid, β-chlorocinnamic acid, β-stearylacrylic acid,itaconic acid, monoalkyl esters of itaconic acid, citraconic acid,mesaconic acid, glutaconic acid, aconitic acid, maleic acid, monoalkylesters of maleic acid, furmaric acid, monoalkyl esters of fumaric acid,dialkyl esters of maleic and fumaric acids, tricarboxyethylene, andmaleic anhydride. Additionally, suitable carboxylic acid monomericcompounds include salts of carboxylic acids, such as alkali metal salts,ammonium salts, amine salts, and so forth. Such salts of carboxylicacids include, for example, sodium (meth)acrylate,trimethylamine(meth)acrylate, triethanolamine-(meth)acrylate, sodiummaleate, methylamine maleate, and so forth.

In some embodiments, a swellable material may include a superabsorbentpolymer that includes an ethylenically unsaturated sulfonic acidmonomeric compound. Suitable ethylenically unsaturated sulfonic acidmonomeric compounds for forming superabsorbent polymers include, forexample, aliphatic or aromatic vinyl sulfonic acids and salts of vinylsulfonic acids; acrylic or methacrylic sulfonic acids and salts ofmethacrylic sulfonic acids; and combinations of any of the foregoing.Exemplary aliphatic or aromatic vinyl sulfonic acids includevinylsulfonic acid, allyl sulfonic acid, vinyl toluene sulfonic acid,and styrene sulfonic acid. Exemplary acrylic and methacrylic sulfonicacids include sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropylacrylate, sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropylsulfonic acid, and 2-acrylamide-2-methylpropane sulfonic acid, and soforth.

Methacrylic acid monomeric compounds may be particularly suitable. Insome embodiments, a swellable material may include a superabsorbentpolymer that includes a methacrylic acid monomeric compound. Someexamples of suitable ethylenically unsaturated methacrylic acidmonomeric compounds include alkyl esters of (meth)acrylic acids, such asethyl (meth)acrylate, methyl (meth)acrylate, butyl (meth)acrylate,2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,hydroxypropyl (meth)acrylate, hydroxy butyl (meth)acrylate, isobornyl(meth)acrylate, lauryl (meth)acrylate, and ethylene glycoldi(meth)acrylate, and so forth.

In some embodiments, ethylenically unsaturated monomeric compounds mayinclude an ethylenically unsaturated beta-hydroxy ester functionalmonomer and an epoxy compound such as a glycidyl ethers and/or glycidylesters. Suitable epoxy compounds include those having the followingstructure:

wherein R is a hydrocarbon radical containing from 4 to 26 carbon atoms.Suitable glycidyl esters include those commercially available from ExxonChemical Company under the designation GLYDEXX-10, or from ShellChemical Company under the designation CARDURA E.

The ethylenically unsaturated monomeric compound(s) are typicallypolymerized in the presence of a crosslinking agent to provide acrosslinked polymer. Suitable crosslinking agents typically possess twoor more groups that are capable of reacting with the ethylenicallyunsaturated monomeric compound and that are at least partially watersoluble or water dispersible, or at least partially soluble ordispersible in an aqueous monomer mixture. Examples of suitablecrosslinking agents may include, for instance, tetraallyloxyethane,N,N′-methylene bisacrylamide, N,N′-methylene bismethacrylamide,triallylamine, trimethylol propane triacrylate, glycerol propoxytriacrylate, divinylbenzene, N-methylol acrylamide, N-methylolmethacrylamide, glycidyl methacrylate, polyethylene polyamines, ethyldiamine, ethyl glycol, glycerin, tetraallyloxyethane and triallyl ethersof pentaerythritol, aluminates, silica, alumosilicates, etc., as well ascombinations thereof. The amount of the crosslinking agent may vary, butis typically present in an amount from about 0.005 to about 1.0 molepercent based on moles of the ethylenically unsaturated monomericcompound(s).

In the embodiments described above, crosslinking generally occurs duringpolymerization. In other embodiments, however, the polymer may contain alatent functional group that is capable of becoming crosslinked whendesired. For instance, the polymer may contain an alkoxysilanefunctional group which, upon exposure to water, forms a silanolfunctional group that condenses to form a crosslinked polymer. Oneparticular example of such a functional group is a trialkoxysilanehaving the following general structure:

wherein R₁, R₂ and R₃ are alkyl groups independently having from 1 to 6carbon atoms. To introduce such a functional group into the polymerstructure, a monomeric compound may be employed that contains thefunctional group, such as an ethylenically unsaturated monomercontaining a trialkoxysilane functional group.

Composite Swellable Materials A. Superabsorbent Particles

Superabsorbent particles include both superabsorbent polymers asdiscussed above, and complexes or mixtures of superabsorbent polymerswith inorganic particles such the inorganic swellable materialsdescribed herein. Similar to the superabsorbent polymers discussedabove, superabsorbent particles formed of complexes or mixtures ofsuperabsorbent polymers with inorganic swellable materials arewater-swellable, water insoluble materials capable of absorbing severaltimes their weight in water. An exemplary superabsorbent particle may becapable of absorbing at least 10 times its weight in distilled water,such as at least 50 times its weight, such as at least 100 times itsweight, such as at least 300 times its weight, such as at least 400times its weight, such as at least 500 times its weight, such as atleast 700 times its weight, such as at least 1,000 times its weight indistilled water.

Superabsorbent particles also include complexes of superabsorbentpolymers and inorganic swellable material. In various embodiments, oneor more inorganic swellable materials may be admixed or crosslinked withone or more superabsorbent polymers. Any one or more types of inorganicswellable material described herein may be admixed or crosslinked with asuperabsorbent polymer. Inorganic swellable materials may be added tosuperabsorbent polymer before, during, and/or after polymerization. Theinorganic swellable material and the superabsorbent polymer may bephysically and/or chemically associated in a form such that the polymercomponent and the inorganic swellable material component are not readilyphysically separable. For example, a superabsorbent polymer particle andan inorganic swellable material may be present in a single particle, asopposed to an admixture of discrete superabsorbent polymer particles anddiscrete inorganic swellable material particles. An exemplarysuperabsorbent composite includes a poly(acrylic acid)- phyllosilicatecomposite. A poly(acrylic acid)-phyllosilicate composite may be formedby graft copolymerization of acrylic acid onto phyllosilicate particles.For example, phyllosilicate particles may be dispersed in an acrylicacid monomer solution, and a crosslinking agent and a cross-linkinginitiator may be added to the dispersed solution.

In one embodiment, an admixture of superabsorbent polymer particles andinorganic swellable material particles may be formed by polymerizing oneor more monomeric components, comminuting the resulting polymer, thenadding the inorganic swellable material to the comminuted polymerparticles. The inorganic swellable material may be added as a powder orin the form of an aqueous slurry. The polymer particles and theinorganic swellable material particles may be admixed, such as byextrusion, to disperse the inorganic swellable material throughout thepolymer. The resulting mixture may be at least partially neutralizedusing a base, comminuted, dried, and sized. Additionally, or in thealternative, the superabsorbent polymer particles and inorganicswellable material particles may be crosslinked (i.e.,surface-crosslinked). For example, a surface crosslinking agent may becombined with the polymer particles and the inorganic swellable materialparticles and the combination subjected to azeotropic dehydration, withcrosslinking occurring during the dehydration.

Suitable surface crosslinking agents include, but are not limited to,glycidyl compounds, such as ethylene glycol diglycidyl ether, diglycidylphosphonates, and bischlorohydrin ethers of polyalkylene glycols;alkoxysilyl compounds; polyaziridines based on polyethers or substitutedhydrocarbons such as bis-N-aziridinomethane; polyamines orpolyamidoamines and their reaction products with epichlorohydrin;carbonic acid derivatives, such as urea, thiourea, guanidine,dicyandiamide, 2-oxazolidinone and its derivatives, bisoxazoline,polyoxazolines, diand polyisocyanates; di- andpoly-N-methylol-compounds, such asmethylenebis(N-methylolmethacrylamide) or melamine-formaldehyde resins;polyols, such as ethylene glycol, 1,2-propanediol, 1,4-butanediol,glycerol, methyltriglycol, polyethylene glycols having an averagemolecular weight Mw of 200-10,000, pentaerythritol, sorbitol, theethoxylates of these polyols and their esters with carboxylic acids orcarbonic acid such as ethylene-carbonate or propylene carbonate; andcompounds having two or more blocked isocyanate groups such as,trimethyl-hexamethylene diisocyanate blocked with2,2,6,6-itetramethylpiperidin-4-one.

In embodiments where the superabsorbent particles contain asuperabsorbent polymer and an inorganic swellable material, thesuperabsorbent particles may contain from 35 wt. % to 95 wt. % of thesuperabsorbent polymer, such as from 50 wt. % to 90 wt. %, such as from65 wt. % to 85 wt. % of the superabsorbent polymer. Conversely, thesuperabsorbent particles may contain from 5 wt. % to 65 wt. % of theinorganic swellable material, such as from 5 wt. % to 60 wt. %, such asfrom 10 wt. % to 40 wt. %, such as from 15 wt. % to 35 wt. % of theinorganic swellable material.

Superabsorbent particles may be porous or non-porous in nature, however,exemplary superabsorbent particles generally possess a porous networkwhich may contain a combination of closed and open-celled pores. Thetotal porosity of the superabsorbent particles may be relatively high.For example, the superabsorbent particles may exhibit a total pore areaof about 2 square meters per gram (m²/g) or more, in some embodimentsfrom 10 to 160 m²/g, such as from 20 to 60 m²/g. The percent porositymay also be about 5% or more, such as 20% to 60%, such as from 25% to40%. Another parameter that is characteristic of porosity is bulkdensity. In this regard, the bulk density of the superabsorbentparticles may be less than 0.8 grams per cubic centimeter (g/cm³), suchas from 0.1 to 0.6 g/cm³, such as from 0.2 to 0.6 g/cm³, as determinedat a pressure of 0.58 psi via mercury intrusion.

B. Coated or Encapsulated Swellable Materials

Another type of composite swellable material includes swellablematerials that have been coated or encapsulated with one or moreencapsulating or coating materials. The encapsulation or coating may beconfigured to prevent or delay the water-swellable properties of theswellable material until a future period or point in time. For example,the encapsulation or coating may prevent or inhibit the swellablematerial from absorbing water or moisture during the manufacturingprocess of the cementitious panel, where water-swellable propertieswould generally be undesirable and may negatively affect crystallizationof the cementitious material or other properties of the panel. In someembodiments, a coating or encapsulation may be capable of dissolving ormelting, such as with exposure to water and/or temperature. For example,a coating or encapsulation may dissolve after having been exposed to acertain amount of water or moisture, such that the swellable materialmay be exposed from the coating or encapsulation with particularly moistor wet conditions. When the coating or encapsulation dissolves, theswellable material within the coating or encapsulation may be exposed,thereby allowing the swellable material to absorb water or moisture thatmay otherwise propagate into the cementitious panel.

As another example, a coating or encapsulation may dissolve or meltunder elevated temperature conditions of a kiln or oven in a typicalmanufacturing process for cementitious panels, such that the swellablematerial may be exposed from the coating or encapsulation after havingpassed through the kiln or oven during manufacturing. In this way, theswellable material may be shielded from moisture or water in themanufacturing process, yet exposed and capable of swelling to prevent ormitigate excessive moisture or water penetration thereafter.

Additionally, or in the alternative, in some embodiments, a coating orencapsulation may be capable of rupturing, for example when thecontinuity of a cementitious panel is interrupted such as by fasteners(e.g., nails, screws, etc.) being driven through the cementitious panelor other sources of punctures, cracks, cuts, perforations, or the like.When the coating or encapsulation ruptures, the swellable materialwithin the coating or encapsulation may be exposed, thereby allowing theswellable material to absorb water or moisture that may otherwisepropagate into the cementitious panel.

Coated or encapsulated swellable materials may be utilized alone ortogether with other swellable materials. In various embodiments, acoated or encapsulated swellable material may be combined with anotherswellable material to provide an admixture or complex. For example, acoated or encapsulated swellable material may be physically and/orchemically associated with another swellable material. Additionally, orin the alternative, a coated or encapsulated swellable material may becrosslinked with one or more other swellable materials.

Suitable swellable materials for forming a coated or encapsulatedswellable material may be selected from any one or more organicswellable materials and/or inorganic swellable materials describedherein. Suitable coating or encapsulating material for forming a coatedor encapsulated swellable material may include wax, ethyl cellulose,polyvinyl alcohol (e.g., fully hydrolyzed polyvinyl alcohol), starch,gelatin, polymeric materials, sodium alginate, epoxy resins, and thelike. Mixtures of any of the organic swellable materials and/orinorganic swellable materials described herein may be used. The specificchoice of swellable materials will depend upon the specific applicationand performance requirements of the coated swellable material. Thethickness of the coating or encapsulation may be selected depending uponthe specific application. For a coating or encapsulation that isintended to dissolve or melt, the thickness of the coating may correlateto the degree of exposure necessary or sufficient to dissolve or meltthe coating or encapsulation. A coating or encapsulation may have amicro-scale thickness or a nano-scale thickness.

In an exemplary embodiment, a coating or encapsulation may have amicro-scale thickness, with an average thickness of from 0.1 to 1,000micrometers, such as from 0.1 to 900 µm, such as from 0.1 to 500 µm,such as from 0.1 to 250 µm, such as from 0.1 to 100 µm, such as from 0.1to 50 µm, such as from 1 to 900 µm, such as from 1 to 100 µm, such asfrom 10 to 500 µm, such as from 10 to 250 µm, such as from 50 to 150 µm,such as from 100 to 250 µm, such as from 250 to 500 µm, such as from 500to 1,000 µm, such as from 500 to 750 µm, such as from 750 to 1,000 µm.The coating or encapsulation may have an average thickness of at least0.1 micrometer, such as at least 1 µm, such as at least 5 µm, such as atleast 10 µm, such as at least 25 µm, such as at least 50 µm, such as atleast 100 µm, such as at least 150 µm, such as at least 250 µm, such asat least 400 µm, such as at least 600 µm, such as at least 800 µm. Thecoating or encapsulation may have an average thickness of less than1,000 micrometer, such as less than 900 µm, such as less than 700 µm,such as less than 600 µm, such as less than 500 µm, such as less than350 µm, such as less than 225 µm, such as less than 175 µm, such as lessthan 125 µm, such as less than 100 µm, such as less than 100 µm, such asless than 75 µm, such as less than 40 µm, such as less than 20 µm, suchas less than 10 µm, such as less than 5 µm.

In an exemplary embodiment, a coating or encapsulation may have anano-scale thickness, with an average thickness of from 0.1 to 1,000nanometers, such as from 0.1 to 900 nm, such as from 0.1 to 500 nm, suchas from 0.1 to 250 nm, such as from 0.1 to 100 nm, such as from 0.1 to50 nm, such as from 1 to 900 nm, such as from 1 to 100 nm, such as from10 to 500 nm, such as from 10 to 250 nm, such as from 50 to 150 nm, suchas from 100 to 250 nm, such as from 250 to 500 nm, such as from 500 to1,000 nm, such as from 500 to 750 nm, such as from 750 to 1,000 nm. Thecoating or encapsulation may have an average thickness of at least 0.1micrometer, such as at least 1 nm, such as at least 5 nm, such as atleast 10 nm, such as at least 25 nm, such as at least 50 nm, such as atleast 100 nm, such as at least 150 nm, such as at least 250 nm, such asat least 400 nm, such as at least 600 nm, such as at least 800 nm. Thecoating or encapsulation may have an average thickness of less than1,000 micrometer, such as less than 900 nm, such as less than 700 nm,such as less than 600 nm, such as less than 500 nm, such as less than350 nm, such as less than 225 nm, such as less than 175 nm, such as lessthan 125 nm, such as less than 100 nm, such as less than 100 nm, such asless than 75 nm, such as less than 40 nm, such as less than 20 nm, suchas less than 10 nm, such as less than 5 nm.

Suitable polymeric materials for forming coated or encapsulatedswellable materials include acrylic polymers (e.g., polyacrylamide,polyacrylate, poly(acrylate-co-acrylamide)), polyvinyl alcohol polymers(e.g., hydrolyzed polyvinyl alcohol), polyamide polymers, polyurethanepolymers, polyester polymers, polyether polymers, silicon-basedpolymers, and co-polymers of any of the foregoing, as well as mixturesof any of the foregoing. In some embodiments, a coated or encapsulatedswellable material can be prepared with one or more ethylenicallyunsaturated monomeric compounds and/or one or more polymers. In oneembodiment, a swellable material may be dispersed in a medium thatcontains a monomeric compound, and the monomeric compound may bepolymerized in the presence of the swellable material. In anotherembodiment, a swellable material may be dispersed in a medium thatcontains a polymeric material that has already been formed. In stillanother embodiment, a swellable material may be admixed with one or moremonomeric compounds and/or polymers. Swellable materials may be coatedor encapsulated using any desired method known in the art, includingphysical or chemical methods. Exemplary physical methods include pancoating and air-suspension coating. Exemplary chemical methods includepolycondensation, cross-linking, and polymerization.

Fire-Resistive Capabilities

In some embodiments, cementitious panels may include one or morematerials that provide fire-resistive properties. Such fire-resistiveproperties may be provided by way of promotion of char formation,forming an intumescent barrier, forming a glaze barrier, and/orconversion of combustible gases to non-flammable gases.

The presently disclosed swellable materials may provide enhancedfire-resistance capabilities. Such enhanced fire-resistance capabilitiesmay be provided by water-swellable materials. By way of example,suitable water-swellable materials for providing enhancedfire-resistance capabilities include high expansion vermiculites,perlite, and calcium silicates.

In some embodiments, a swellable material may exhibit intumescentproperties, meaning that the swellable material may swell when exposedto heat. Such swelling may close gaps, cracks, pores, and the like in acementitious panel, restricting air flow needed for combustion. Anintumescent material may also exhibit low thermal conductivity, reducingthe transfer of heat from a fire through a cementitious panel.Additionally, or in the alternative, an intumescent material may alsorelease water vapor when heated, which may be absorbed by waterswellable materials, providing further swelling so as to restrict airflow through gaps, cracks, pores, and the like in a cementitious panel.

Exemplary intumescent materials include microporous carbonaceous softchar materials and/or hard char materials. Soft char materials may beformed from a combination of ammonium polyphosphate, pentaeyrthritol,and melamine, with a binder of vinyl acetate or styrene acrylate binder.Hard char materials include sodium silicates graphite.

In addition, or as an alternative to swellable/intumescent materials,exemplary cementitious panels may include a filler material thatprovides fire-resistive properties. For example, a filler material mayundergo an endothermic decomposition reaction when exposed to flames orheat. Such materials may release free water as a result of endothermicdecomposition, and the free water may be absorbed by water swellablematerials. Exemplary endothermic materials include aluminum trihydroxide(ATH) and magnesium hydroxide. As another example, a filler material mayoxidize when exposed to flames or heat, producing carbonaceous charwhich may prevent further combustion. Exemplary oxidizing materialsinclude phosphates such as ammonium dihydrogenphosphate, ammoniumphosphate, and/or urea phosphate.

VOC Removal Properties

In some embodiments, exemplary cementitious panels may contain one ormore materials that provide VOC adsorbing properties. One or more of thepresently disclosed swellable materials or filler materials may provideVOC adsorbing properties. Exemplary materials with VOC adsorbingcapabilities may include activated carbon, carbonates, bicarbonates,carbon black, aluminosilicates (i.e., zeolite, hylloysite, etc.),nano-crystalline metal oxides/hydroxides, coated metal oxides/hydroxides(i.e., halogen coatings), doped metal oxides/hydroxides, surfactantcoated nanocrystalline metal oxides, mesoporous nanocrystalline metaloxides, aluminophosphates, mesoporous silica, ethylene urea and itsderivatives, clays or siliceous particles (e.g., vermiculite, silicagel, etc.), and/or hydrazide compounds.

In some embodiments, a cementitious panel may additionally oralternatively include a coating that contains one or more photocatalyticmaterials capable of converting VOCs to harmless substances in thepresence of UV or other light irradiation. Exemplary photocatalyticmaterials include titanium dioxide and mesoporous titanium dioxide.Titanium dioxide may be doped with one or more doping agents such asnitrogen, iron, silver, palladium, platinum, cerium, zirconium, or zinc.The photocatalytic reaction may be catalyzed by a suitable light sourceincluding artificial or natural light, including UV light, florescentlight, visible light, black light, and/or a combination thereofdepending on the particular photocatalyst.

Void Volumes

A cementitious panel may include void volumes having a variety ofdifferent characteristics. A cementitious core material may include voidvolumes resulting from foam introduced into the core material to lowerthe density of the material. A dense layer may include similar voidvolumes introduced by foam. A facing material may include void volumesin the form of a porous network or interconnected network of pores. Thevoid volumes or pores in a facing material may be formed as a result ofthe manner in which the facing material was produced. For example, afacing material may include a polymeric-film may formed of athermoplastic composition that includes a polymer matrix and a swellablematerial. The thermoplastic composition may be drawn so as to form aporous network of interconnected pores. Additionally, the swellablematerial may itself contain pores. As another example, a facing materialformed of paper or paperboard, or woven or non-woven fibers or filamentsmay include void volumes or a network of interconnected pores locatedbetween adjacent fibers or filaments or other such materials.

In some embodiments, the average percent volume occupied by the voidvolumes or pores within a given unit volume of a particular segment of acementitious panel (e.g., the core layer, the dense layer, or the facingmaterial) may be from 5% to 85% per cm³, such as from 5% to 50% per cm³,such as from 5% to 30% per cm³, such as from 5% to 20% per cm³, such asfrom 20% to 50% per cm³, such as from 20% to 70% per cm³, such as from30% to 60% per cm³ of such segment.

The void volumes may be of a nano-scale size, a micro-scale size, and/ora macro-scale size. In some embodiments, nano-scale void volumes mayhave an average cross-sectional dimension from 5 nm to less than 1000nm, such as from 5 nm to 900 nm, such as from 10 nm to 500 nm, such asfrom 50 nm to 250 nm, such as 1000 nm or less, such as 900 nm or less,such as 700 nm or less, such as 500 nm or less, such as 250 nm or less,such as 150 nm or less, such as 100 nm or less, such as 75 nm or less,such as 50 nm or less, such as 10 nm or less. The void volumes may havean average cross-sectional dimension of 5 nm to 900 nm or less, such as25 nm or more, such as 50 nm or more, such as 75 nm or more, such as 100nm or more, such as 250 nm or more, such as 500 nm or more, such as 750nm or more. The term “cross-sectional dimension” generally refers to acharacteristic dimension (e.g., width or diameter) of a volume, which issubstantially orthogonal to its major axis (e.g., length). The voidvolumes may also have an average axial dimension within a range from 10nm to 5000 nm, such as from 50 nm to 2000 nm, such as from 100 nm to1000 nm. The “axial dimension” is the dimension in the direction of themajor axis (e.g. length).

Micro-scale void volumes may have an average cross-sectional dimensionfrom 1 µm to 20 µm, such as from 5 µm to 15 µm, such as from 1 µm to 10µm, such as from 2 µm to 5 µm, such as 15 µm or less, such as 12 µm orless, such as 9 µm or less, such as 7 µm or less, such as 5 µm or less,such as 3 µm or less. The void volumes may have an averagecross-sectional dimension of 1 µm to 20 µm or less, such as 1 µm ormore, such as 5 µm or more, such as 10 µm or more, such as 15 µm ormore.

Macro-scale void volumes may have an average cross-sectional dimensionfrom 1 mm to 10 mm, such as from 1 mm to 9 mm, such as from 1 mm to 7mm, such as from 2 mm to 5 mm, such as 10 mm or less, such as 8 mm orless, such as 5 mm or less, such as 3 mm or less, such as 2 mm or less.The void volumes may have an average cross-sectional dimension of 1 mmto 10 mm or less, such as 1 mm or more, such as 3 mm or more, such as 5mm or more, such as 7 mm or more.

A cementitious panel may include a facing material that is substantiallyimpervious to liquid water yet “breathable” in the sense of beingpervious to water vapor and gases. The “breathability” of the facingmaterial may be measured in terms of water vapor transmission rate(WVTR), which generally refers to the rate at which water vaporpermeates through a material as measured in units of grams per metersquared per 24 hours (g/m²/24 hrs). Higher WVTR values represent a morebreathable material and lower WVTR values represent a less breathablematerial. The test used to determine the WVTR of a material may varybased on the nature of the material. For example, one technique formeasuring WVTR involves the use of a PERMATRAN-W 100 K water vaporpermeation analysis system, which is commercially available from ModernControls, Inc. of Minneapolis, MN. Such a system may be particularlywell suited for materials thought to have a WVTR of greater than about2,000 g/m²/24 hrs. It should be understood, however, that other systemsand techniques for measuring WVTR may also be utilized in the presentinvention. Another technique for measuring WVTR is provided by ASTM E96,Standard Test Methods for Water Vapor Transmission of Materials.

An exemplary facing material may exhibit a surface water resistanceaccording to ASTM C-473 such that the panel absorbs less than 10% ofwater, such as less than 7.5%, less than 5%, less than 1%, or less than0.5%, or less than 0.25%. Regardless, a breathable facing materialshould have sufficient permeability to allow for water vapor to passthrough when drying the panels in the oven or kiln. In an exemplaryembodiment, the pore structure of the facing material allows it toexhibit a high breathability, such as a WVTR of about 100 to about10,000 grams/m²-24 hours, such as about 500 to about 10,000 grams/m²-24hours, such as about 1,000 to about 10,000 grams/m²-24 hours, such asabout 1,000 to about 6,000 grams/m²-24 hours, such as about 1,000 toabout 5,000 grams/m²-24 hours, such as about 5,000 to about 10,000grams/m²-24 hours, such as about 5,000 to about 7,000 grams/m²-24 hours,such as about 7,000 to about 10,000 grams/m²-24 hours, such as about 100grams/m²-24 hours or more, such as about 500 grams/m²-24 hours or more,such as about 1,000 grams/m²-24 hours or more, such as about 2,000grams/m²-24 hours or more, such as about 5,000 grams/m²-24 hours ormore, such as about 7,000 grams/m²-24 hours or more, or such as about10,000 grams/m²-24 hours or more. The facing material may also limit theamount of liquid water that passes therethrough upon the application ofpressure, i.e., it resists a hydrostatic pressure (“hydrohead”) of about50 millibar or more, in some embodiments about 70 millibar or more, insome embodiments about 80 millibar or more, and in some embodiments,about 100 millibar or more without allowing liquid water to pass. Anon-breathable facing material may exhibit a WVTR of less than about 100grams/m²-24 hours, such as less than 50 grams/m²-24 hours, such as lessthan 25 grams/m²-24 hours.

A breathable facing material may exhibit a porosity from 10 to 20,000sec/100 cc air, as determined according to ASTM D 726, such as from 10to 100 sec/100 cc air, such as from 100 to 1,000 sec/100 cc air, such asfrom 1,000 to 5,000 sec/100 cc air, such as from 5,000 to 10,000 sec/100cc air, such as from 1,000 to 10,000 sec/100 cc air, such as from 10,000to 15,000 sec/100 cc air, such as from 15,000 to 20,000 sec/100 cc air,such as from 10,000 to 20,000 sec/100 cc air. The facing material mayexhibit a porosity greater than 10 sec/100 cc air, such as greater than50 sec/100 cc air, such as greater than 100 sec/100 cc air, such asgreater than 200 sec/100 cc air, such as greater than 500 sec/100 ccair, such as greater than 1,000 sec/100 cc air, such as greater than2,500 sec/100 cc air, such as greater than 5,000 sec/100 cc air, such asgreater than 7,500 sec/100 cc air, such as greater than 10,000 sec/100cc air, such as greater than 12,500 sec/100 cc air, such as greater than15,000 sec/100 cc air. The facing material may exhibit a porosity lessthan 20,000 sec/100 cc air, such as less than 15,000 sec/100 cc air,such as less than 12,500 sec/100 cc air, such as less than 10,000sec/100 cc air, such as less than 7,500 sec/100 cc air, such as lessthan 5,000 sec/100 cc air, such as less than 2,500 sec/100 cc air, suchas less than 1,000 sec/100 cc air, such as less than 500 sec/100 cc air,such as less than 200 sec/100 cc air, such as less than 100 sec/100 ccair, such as less than 50 sec/100 cc air. A non-breathable facingmaterial may exhibit a porosity from 25,000 sec/100 cc air to 200,000sec/100 cc air, as determined according to ASTM D 726, such as from50,000 to 100,000 sec/100 cc air.

Manufacturing System

Now referring to FIG. 3 , an exemplary system 300 for manufacturingcementitious panels is shown. The exemplary system 300 includes aconveyor assembly 302 such as a continuous belt or fabric, acementitious core material supply manifold 304 positioned above asurface of the continuous belt or fabric of the conveyor assembly 302.The cementitious core material supply manifold 304 includes an outlet306 such as a chute or “boot” configured to apply a slurry ofcementitious core material 308 so as apply a layer of cementitious corematerial 308 which will be formed into the core layer 102 of acementitious panel 100. The slurry of cementitious core material 308 maybe provided from a mixing apparatus 310, such as a pin mixer. The slurryof cementitious core material 308 may be provided by mixing dry and wetingredients in the mixing apparatus 310. The dry ingredients caninclude, but are not limited to, any combination of cementitiousmaterial such as calcium sulfate hemihydrate and known additives, suchas fiberglass, accelerator, and in some cases natural or syntheticpolymers (e.g., starch). The wet ingredients can be made of manycomponents, including but not limited to, surfactants, dispersants,defoamers, retarders, rheology modifiers, a mixture of water, paperpulp, and other additives, such as potash and natural or syntheticpolymer (e.g., starch). The exemplary system 300 further includes afacing material supply assembly 312 configured to supply to the conveyorassembly 302 a plurality of sheets of facing material 104 from aplurality of facing material supply rolls 314. In one embodiment, theplurality of sheets of facing material include an upper sheet and alower sheet. For purposes of convenience, the lower sheet refers to thesheet of facing material that is closer to the conveyor assembly 302,and the upper sheet refers to the sheet of facing material that isfurther away from the conveyor assembly. Typically, cementitious panelsare formed front-side down, such that the lower sheet corresponds to thefront-side of the panel. However, cementitious panels may also be formedback-side down, such that the lower sheet corresponds to the back-sideof the panel. The exemplary embodiments that follow describe a systemfor manufacturing cementitious panels in which the panels are formedfront-side down. However, these examples are provided by way ofillustration only and should not be interpreted at limiting the presentdisclosure.

As shown in FIG. 3 , a lower facing material supply assembly 316supplies a lower sheet of facing material 318 to the conveyor assembly302 from a lower facing material supply roll 320. An upper facingmaterial supply assembly 322 supplies an upper sheet of facing material324 to the conveyor assembly 302 from an upper facing material supplyroll 326. The slurry of cementitious core material 308 flows from theoutlet 306 and spreads onto a moving continuous lower sheet of facingmaterial 318, while a moving continuous upper sheet of facing material314 is applied on the slurry of cementitious material 308. The exemplarysystem 300 may further include a dense layer applicator assemblyconfigured to apply a dense layer 110 to the upper sheet of facingmaterial 324 and/or to the lower sheet of facing material 318 upstreamfrom the supply manifold 304.

As shown, the system 300 includes an upper dense layer applicatorassembly 328 and a lower dense layer applicator assembly 330. The upperdense layer applicator assembly 328 may include for example, a rollerassembly and/or a nozzle assembly configured to apply a slurry ofcementitious material 308 to the inward side of the upper sheet offacing material 324 in a manner such that the slurry forms a dense layer110. Similarly, the lower dense layer applicator assembly 330 mayinclude for example, a roller assembly and/or a nozzle assemblyconfigured to apply a slurry of cementitious material 308 to the inwardside of the lower sheet of facing material 318 in a manner such that theslurry forms a dense layer 110.

The slurry of cementitious material 308 used to form a dense layer maybe of similar composition to that used to form the core layer 102 exceptthat the dense layer typically exhibits a greater concentration ofgypsum crystals and a lower concentration of void volumes. This may beaccomplished through the manner in which the slurry of cementitiousmaterial 308 is applied when forming the dense layer 110. For example,the dense layer applicator assembly may be configured to reduce minimizethe introduction of air that may generate foam. Additionally, or in thealternative, the concentration of wet ingredients (e.g., defoamer ordispersant) may be modified to achieve the desired dense layerproperties. In some embodiments, the slurry of cementitious material 308used to form the dense layer may be supplied to the upper and/or lowerdense layer applicator assembly 328, 330 from the same mixing apparatus310 from which cementitious material 308 is supplied to the supplymanifold 304. Alternatively, a separate or additional mixing apparatus(not shown) may be utilized to supply cementitious material to the upperand/or lower dense layer applicator assembly 328, 330. For example, aseparate or additional mixing apparatus may be utilized when desiring toinclude different ingredients or different concentrations of ingredientsin the dense layer 110.

The exemplary system 300 further includes a forming assembly 332configured to form a continuous length of cementitious panel material334 to a desired thickness and width. At the forming assembly, the lowersheet of facing material 318 and/or the upper sheet of facing material324 may be folded, wrapped, and/or pressed, or the like, so as tosurround the slurry of cementitious core material 308. For example, thelower sheet of facing material 318 may wrap around the slurry ofcementitious core material 308 and onto the upper sheet of facingmaterial 324. Alternatively, or in addition, the upper sheet of facingmaterial 324 may wrap around the slurry of cementitious core material308 and onto the lower sheet of facing material 318. An adhesive may beutilized for adhering the upper sheet of facing material and the lowersheet of facing material 318 to one another.

In some embodiments, the exemplary system may include a coater assemblysystem configured to apply a coating to the upper sheet of facingmaterial 324 and/or to the lower sheet of facing material 318. As shown,the system 300 includes an upper coater assembly 336 and a lower coaterassembly 338. The upper coater assembly 336 may include for example, aroller assembly and/or a nozzle assembly configured to apply a coatingto the outward side of the upper sheet of facing material 324.Similarly, the lower coater assembly 338 may include for example, aroller assembly and/or a nozzle assembly configured to apply a coatingto the outward side of the lower sheet of facing material 318. Such acoating may be applied to the upper or lower sheet of facing material324, 318 so as to provide a facing material 104 with a plurality oflayers. For example, a facing material 104 may include a first layer 116of facing material 104 applied to a second layer 118 of facing material104 using a coater assembly 336, 338. The upper coater assembly 336and/or the lower coater assembly 338 may be located either upstream ordownstream from the forming assembly 332. As shown, the upper coaterassembly 336 is located downstream from the forming assembly 332 and thelower coater assembly 338 is located upstream from the forming assembly332. A coater assembly 336, 338 may be desirable for providing coatingswith different formulations or properties, such as formulations orproperties that may vary as between different grades of cementitiouspanels 100. Alternatively, or in addition, cementitious panels may beformed using facing material that has already been coated. For example,the facing material supply rolls 314 may supply a facing material thathas a plurality of layers, including a coated facing material.

Swellable materials may be included in the core layer 102, the facingmaterial 104, and/or the dense layer 110 of a cementitious panel 100.The swellable material may be supplied from a storage tank (not shown),which may be provided in the form of a permanent tank, a portable tote,or rolling stock equipped with a tank or tote. In some embodiments,swellable material may be introduced into the mixing apparatus 310 as adry ingredient and/or as a wet ingredient. A slurry of cementitious corematerial 308 supplied from the mixing apparatus 310 may thereby includea swellable material. A slurry cementitious core material 308 thatincludes a swellable material may be supplied to the supply manifold 304so as to form cementitious panels 100 that include swellable material inthe core layer 102. Additionally, or in the alternative, a slurrycementitious core material 308 that includes a swellable material may besupplied to the upper dense layer applicator assembly 328 and/or to thelower dense layer applicator assembly 330 so as to form cementitiouspanels 100 that include swellable material in the dense layer 110.

In some embodiments, a swellable material may be introduced to the upperdense layer applicator assembly 328 and/or to the lower dense layerapplicator assembly 330 through a dense layer supply line. As shown, anupper dense layer supply line 340 may supply a swellable material to theupper dense layer applicator assembly 328, and a lower dense layersupply line 342 may supply a swellable material to the lower dense layerapplicator assembly 330. The upper dense layer supply line 340 and/orthe lower dense layer supply line 342 may be utilized to introduceswellable material to the corresponding dense layer(s) in differentquantities than that of the central core layer 103 and/or to introduceswellable material to the dense layer(s) that differ in composition fromswellable material introduced into the central core layer 103. Forexample, in one embodiment, a swellable material may be included in thedense layer(s) without including the swellable material in the centralcore layer 103. In another embodiment, the dense layer(s) may include afirst swellable material and the central core layer 103 may include asecond swellable material, in which the first swellable material differsfrom the second swellable material in respect of concentration and/orcomposition.

In some embodiments, a swellable material may be introduced to the uppercoater assembly 336 and/or to the lower coater assembly 338 through acoater assembly supply line. As shown, an upper coater assembly supplyline 344 may supply a swellable material to the upper coater assembly336, and a lower coater assembly supply line 346 may supply a swellablematerial to the lower coater assembly 338. In some embodiments, theupper coater assembly 336 may be used to introduce a swellable materialto the upper sheet of facing material 324 and/or the lower coaterassembly 338 may be used to introduce a swellable material to the lowersheet of facing material 318. Additionally, or in the alternative,cementitious panels may be formed using facing material that alreadyincludes swellable material. For example, the facing material supplyrolls 314 may supply a facing material that includes a swellablematerial.

After passing through the forming assembly 332, the continuous length ofcementitious panel material 334 is cut with a cutting device 348 such asa saw blade, water knife, or other suitable device to provide a seriesof sequential cementitious panels 350 of a desired length. Typically,the cutting device 348 will be positioned a sufficient distancedownstream from the forming assembly 332 such that the core material hasset sufficiently to retain its shape. In some embodiments, vacuum boxesmay be positioned along the conveyor assembly 302 to remove excesswater.

The cementitious panels 350 continue along the conveyor assembly 302 forsome distance, allowing the cementitious core material to further cure.Typically, the cementitious panels 350 are formed front-side down, andafter the cementitious panels 350 have sufficiently cured, they aretypically turned front-side up at a wet transfer table 352 to protectthe front side of the panels from being damaged by the conveyor assembly302. The wet transfer table 352 may include an articulating lifting andlowering mechanism 354, which has a first set of forks or arms that liftthe cementitious panel from its first broad face onto its edge, and asecond set of forks or arms that lower the cementitious panel onto itsopposite side, bringing the cementitious panel to rest on its secondbroad face. The cementitious panels 350 are dried in an oven or kiln 356or other suitable drying apparatus to evaporate excess (free) waterwhile chemically bound water is retained in gypsum crystals formedthrough the curing process. The cementitious panels 350 are typicallydried front-side up, as the wet transfer table 352 with an articulatinglifting and lowering mechanism 354 is typically provided to turn thecementitious panel over prior to heating the cementitious panel in theoven or kiln 356. Typically, the cementitious core material 308partially sets prior to being heated in the oven or kiln 356, and thenfurther at least partially sets during heating in the oven or kiln 356.After exiting the oven or kiln 356, dried cementitious panels 358 arebundled in pairs of two or as needed, with front-sides facing oneanother, at a dry transfer table 360. The dry transfer table typicallyincludes a similar articulating lifting and lowering mechanism 362,which lifts and lowers a first cementitious panel on top of a secondcementitious panel. The dried panels 358 may be further cut to desiredsizes and bundled together for transfer to a warehouse or for shipping,using various forms of finishing equipment 364.

Now turning to FIGS. 4A and 4B, exemplary methods of manufacturingcementitious panels will be discussed. Exemplary methods may beperformed using the exemplary system 300 described herein, including anycombination or arrangement of various features of such a system.Additionally, exemplary methods may be performed to make any of thecementitious panels described herein, including any combination orarrangement of various features of such panels. As shown in FIG. 4A, insome embodiments, an exemplary method 400 includes conveying with aconveyor assembly, a plurality of sheets of facing material and a slurryof cementitious core material that contains a swellable material 402.The plurality of sheets of facing material include a first sheet offacing material and a second sheet of facing material, with the firstsheet of facing material being an upper sheet of facing material and thesecond sheet of facing material being a lower sheet of facing material.The exemplary method 400 may proceed by forming, with a formingassembly, a continuous length of cementitious panel material comprisingthe slurry of cementitious core material surrounded by the plurality ofsheets of facing material 404, and cutting the continuous length ofcementitious panel material laterally to a desired length, providing acementitious panel 406.

In some embodiments, the exemplary method 400 may optionally includecombining a swellable material in a slurry of cementitious core material408. The slurry of cementitious core material containing the swellablematerial may be mixed with a mixing apparatus 310, such as a pin mixer.The slurry of cementitious core material containing the swellablematerial may be supplied to a supply manifold 304, and the supplymanifold may apply a layer of cementitious core material 308 to beformed into the core layer 102 of a cementitious panel 100. In someembodiments, the exemplary method 400 may additionally or alternativelyinclude applying the slurry of cementitious core material containing theswellable material to an inner surface of any one or more of a pluralityof sheets of facing material 410. The slurry of cementitious corematerial containing the swellable material may be applied to such innersurface using a dense layer applicator assembly 328, 330 such that theslurry forms a dense layer 110.

Another exemplary method 450 of manufacturing a cementitious panel willbe discussed with reference to FIG. 4B. The exemplary method 450 may beperformed alone or in combination with the exemplary method 400 of FIG.4A. Likewise, any one or more steps of the exemplary method 400 of FIG.4A may be combined with any one or more steps of the exemplary method450 of FIG. 4B. As shown in FIG. 4B, in some embodiments, an exemplarymethod 450 includes conveying with a conveyor assembly, a slurry ofcementitious core material and a plurality of sheets of facing materialin which at least one of the plurality of sheets of facing materialinclude a swellable material 452. The plurality of sheets of facingmaterial may include a first sheet of facing material and a second sheetof facing material, with the first sheet of facing material being anupper sheet of facing material and the second sheet of facing materialbeing a lower sheet of facing material. The exemplary method 450 mayproceed by forming, with a forming assembly, a continuous length ofcementitious panel material comprising the slurry of cementitious corematerial surrounded by the plurality of sheets of facing material 454,and cutting the continuous length of cementitious panel materiallaterally to a desired length, providing a cementitious panel 456.

In some embodiments, the exemplary method 450 may optionally includecombining a swellable material in a slurry of cementitious core material458. The slurry of cementitious core material containing the swellablematerial may be mixed with a mixing apparatus 310, such as a pin mixer.The slurry of cementitious core material containing the swellablematerial may be supplied to a supply manifold 304, and the supplymanifold may apply a layer of cementitious core material 308 to beformed into the core layer 102 of a cementitious panel 100. In someembodiments, the exemplary method 450 may additionally or alternativelyinclude applying a coating to one or more of a plurality of sheets offacing material, in which the coating includes a swellable material 460.The coating may be applied to an inner surface or an outer surface of asheet of facing material. In some embodiments, the coating may beapplied using a coater assembly, such as an upper coater assembly 336and/or a lower coater assembly 338. The coating may provide a facingmaterial 104 with a plurality of layers such as a first layer 116 offacing material 104 that includes a swellable material applied to asecond layer 118 of facing material 104. Alternatively, or in addition,an exemplary method 450 may utilize a facing material that has alreadybeen coated and/or that already includes a swellable material.

Referring to both FIGS. 4A and 4B, in some embodiments, the swellablematerial may include an encapsulation or coating configured to preventor delay the water-swellable properties of the swellable material untila future period or point in time. An exemplary method 400, 450 mayinclude dissolving a coating or encapsulation layer of the swellablematerial with exposure to a first quantity of water or moisture so as toexpose at least a portion of the swellable material 412, 462.Additionally, or in the alternative, an exemplary method 400, 450 mayinclude melting or dissolving a coating or encapsulation layer of theswellable material in an oven or kiln while drying the cementitiouspanel so as to expose at least a portion of the swellable material 414,462.

Now turning to FIG. 5 , exemplary methods of providing a moisture orwater barrier in a cementitious panel will be discussed. An exemplarymethod 500 includes contacting a swellable material in a cementitiouspanel with a first quantity of moisture or water 502, and absorbing withthe swellable material at least some of the first quantity of moistureor water with the swellable material swelling to at least twice thenon-swollen volume of the swellable material 504. The moisture or watermay come into contact with the swellable material through void volumesin the cementitious panel (e.g., pores in the facing material), and/orthrough holes, punctures, cracks, cuts, perforations, or the like whichmay arise from damage to a cementitious panel as well as from ordinaryinstallation, use, or wear. For example, water or moisture may penetratethrough holes, punctures, cracks, cuts, perforations, or the like causedby fasteners, thereby coming into contact with the swellable material.

The exemplary method 500 continues with at least partially blocking avoid volume in the cementitious panel with the swellable materialswollen from having absorbed at least some of the first quantity ofwater 506, and preventing or mitigating a second quantity of moisture ofwater from penetrating through the void volume at least partiallyblocked by the swollen swellable material 508. The void volume mayinclude a porous structure of the cementitious panel, and/or such holes,punctures, cracks, cuts, perforations, or the like through which thewater or moisture was absorbed or which may be located near the swollenswellable material. In some embodiments, the void volume may include afastener hole. In some embodiments, the exemplary method 500 may includedesorbing at least some of the first quantity of moisture from theswellable material under conditions exhibiting a lesser degree ofmoisture of water exposure than conditions when the swellable materialabsorbed at least some of the first quantity of moisture 510.

In some embodiments, the swellable material may include an encapsulationor coating configured to prevent or delay the water-swellable propertiesof the swellable material until a future period or point in time. Anexemplary method 500 may include rupturing an encapsulation or coatinglayer of a swellable material in a cementitious panel 512. For example,an encapsulation or coating layer may be ruptured by fasteners such asnails or screws penetrating the cementitious panel when hanging thecementitious panel in place. Additionally, or alternatively, anencapsulation or coating layer may be ruptured by other objects that maycause such punctures, cracks, cuts, perforations, or the like. Inanother embodiment, an exemplary method 500 may additionally oralternatively include melting or dissolving a coating or encapsulationlayer of the swellable material 514. For example, the coating orencapsulation layer may be dissolved with exposure to a first quantityof water or moisture so as to expose at least a portion of the swellablematerial 412, 462. Additionally, or in the alternative, the coating orencapsulation layer of the swellable material may be melted or dissolvedin an oven or kiln while drying the cementitious panel so as to exposeat least a portion of the swellable material 414, 462.

This written description uses exemplary embodiments to describe thepresently disclosed subject matter, including the best mode, and also toenable any person skilled in the art to practice such subject matter,including making and using any devices or systems and performing anyincorporated methods. The patentable scope of the presently disclosedsubject matter is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is: 1-69. (canceled)
 70. A cementitious panel,comprising: a core layer comprising a cementitious material; a pluralityof sheets of facing material surrounding the core layer, the pluralityof sheets of facing material comprising a first sheet of facing materialand a second sheet of facing material; a first dense layer comprising acementitious material defining an interface between the core layer andthe first sheet of facing material; and one or more swellable materialscomprising a clay, wherein the first dense layer comprises at least oneswellable material of the one or more swellable materials.
 71. Thecementitious panel of claim 70, wherein the core layer further comprisesat least one swellable material of the one or more swellable materials,the one or more swellable materials of the core layer comprising from0.1 wt. % to 90 wt. % of the core layer, based on the total weight ofthe core layer.
 72. The cementitious panel of claim 70, wherein thefirst dense layer comprises the one or more swellable materials in anamount of from 0.1 wt. % to 90 wt.% based on the total weight of thefirst dense layer.
 73. The cementitious panel of claim 70, wherein theone or more swellable materials comprise particles and/or discretedomains of a micro-scale size, the particles and/or discrete domainshaving an average cross-sectional dimension from 1 µm to 2000 µm. 74.The cementitious panel of claim 70, wherein the one or more swellablematerials comprise particles and/or discrete domains of a nano-scalesize, the particles and/or discrete domains having an averagecross-sectional dimension from 1 nm to 1,000 nm.
 75. The cementitiouspanel of claim 70, wherein the one or more swellable materials have thecapability to swell to a volume that is from 2 to 100 times thenon-swollen volume of the one or more swellable materials.
 76. Thecementitious panel of claim 70, wherein the one or more swellablematerials have the capability to absorb from 2 to 30 times its weight indistilled water.
 77. The cementitious panel of claim 70, wherein the oneor more swellable materials comprise one or more phyllosilicates. 78.The cementitious panel of claim 77, wherein at least one of the one ormore phyllosilicates comprises bentonite.
 79. The cementitious panel ofclaim 70, wherein the one or more swellable materials comprise anencapsulated or coated swellable material.
 80. The cementitious panel ofclaim 70, wherein the cementitious panel exhibits a surface waterresistance according to ASTM C-473 such that the cementitious panelabsorbs less than 10% of water.
 81. The cementitious panel of claim 70,wherein the cementitious panel comprises void volumes in the form of oneor more holes, punctures, cracks, cuts, or perforations, at least someof the void volume at least partially blocked by the one or moreswellable materials having been swollen by absorbing water or moisture,wherein the holes optionally include fastener holes.
 82. Thecementitious panel of claim 70, wherein the cementitious panel furthercomprises a second dense layer.
 83. A method of providing a moisture orwater barrier in a cementitious panel, the method comprising: contactingone or more swellable materials in a cementitious panel with a firstquantity of moisture or water, the one or more swellable materialscomprising a clay; absorbing with the one or more swellable materials atleast some of the first quantity of moisture or water with the one ormore swellable materials swelling to at least twice the non-swollenvolume of the one or more swellable materials; at least partiallyblocking a void volume in the cementitious panel with the one or moreswellable materials swollen from having absorbed at least some of thefirst quantity of water; and preventing or mitigating a second quantityof moisture of water from penetrating through the void volume at leastpartially blocked by the one or more swollen swellable materials. 84.The method of claim 83, wherein the void volume comprises one or moreholes, punctures, cracks, cuts, or perforations.
 85. The method of claim83, wherein the void volume comprises one or more fastener holes.
 86. Acementitious panel, comprising: a core layer comprising a cementitiousmaterial; a plurality of sheets of facing material surrounding the corelayer, the plurality of sheets of facing material comprising a firstsheet of facing material and a second sheet of facing material; a firstdense layer comprising a cementitious material defining an interfacebetween the core layer and the first sheet of facing material, the firstdense layer formed by applying the cementitious material to an innerside of the first sheet of facing material, the first dense layer havinga higher concentration of gypsum crystals and a lower concentration ofvoid volumes than the core layer, wherein at least a portion of thefirst dense layer penetrates into the first sheet of facing material;and one or more swellable materials comprising a clay, wherein the firstdense layer comprises at least one swellable material of the one or moreswellable materials.
 87. The cementitious panel of claim 86, wherein thecore layer further comprises at least one swellable material of the oneor more swellable materials, the one or more swellable materials of thecore layer comprising from 0.1 wt. % to 90 wt. % of the core layer,based on the total weight of the core layer.
 88. The cementitious panelof claim 86, wherein the first dense layer comprises the one or moreswellable materials in an amount of from 0.1 wt. % to 90 wt.% based onthe total weight of the first dense layer.
 89. The cementitious panel ofclaim 86, wherein the one or more swellable materials comprise particlesand/or discrete domains of a micro-scale size, the particles and/ordiscrete domains having an average cross-sectional dimension from 1 µmto 2000 µm.
 90. The cementitious panel of claim 86, wherein the one ormore swellable materials comprise particles and/or discrete domains of anano-scale size, the particles and/or discrete domains having an averagecross-sectional dimension from 1 nm to 1,000 nm.
 91. The cementitiouspanel of claim 86, wherein the one or more swellable materials have thecapability to swell to a volume that is from 2 to 100 times thenon-swollen volume of one or more swellable materials.
 92. Thecementitious panel of claim 86, wherein the one or more swellablematerials have the capability to absorb from 2 to 30 times its weight indistilled water.
 93. The cementitious panel of claim 86, wherein the oneor more swellable materials comprise one or more phyllosilicates. 94.The cementitious panel of claim 93, wherein at least one of the one ormore phyllosilicates comprises bentonite.
 95. The cementitious panel ofclaim 86, wherein the one or more swellable materials comprise anencapsulated or coated swellable material.
 96. The cementitious panel ofclaim 86, wherein the cementitious panel exhibits a surface waterresistance according to ASTM C-473 such that the cementitious panelabsorbs less than 10% of water.